Amicus Curiae Brief — United Airlines, Incorporated, Petitioner v. Genise Kincannon, Individually and on Behalf of All Others Similarly Situated, et al.

No. 26-183

In the Supreme Court of the United States

________________________________________

UNITED AIRLINES, INC., PETITIONER

v.

GENISE KINCANNON, INDIVIDUALLY AND ON BEHALF OF

ALL OTHERS SIMILARLY SITUATED, ET AL.

________________________________________

ON PETITION FOR A WRIT OF CERTIORARI

TO THE UNITED STATES COURT OF APPEALS

FOR THE FIFTH CIRCUIT

________________________________________

BRIEF OF AIRLINES FOR AMERICA AS

AMICUS CURIAE SUPPORTING PETITIONER

________________________________________

Shay Dvoretzky

Counsel of Record

Parker Rider-Longmaid

Alexander M. Johnson

Alisha Nanda

SKADDEN, ARPS, SLATE,

Emily Jennings

MEAGHER & FLOM LLP

SKADDEN, ARPS, SLATE, 1440 New York Ave. NW

MEAGHER & FLOM LLP Washington, DC 20005

500 Boylston St.

202-371-7000

shay.dvoretzky@skadden.com

Boston, MA 02116

Douglas Mullen

Riva Parker

AIRLINES FOR AMERICA

1275 Pennsylvania

Ave. NW

Washington, DC 20004

Raza Rasheed

SKADDEN, ARPS, SLATE,

MEAGHER & FLOM LLP

2000 Ave. of the Stars,

Ste. 200N

Los Angeles, CA 90067

Counsel for Amicus Curiae

i

TABLE OF CONTENTS

Page

TABLE OF AUTHORITIES ...................................... iii

INTERESTS OF AMICUS CURIAE .......................... 1

INTRODUCTION AND SUMMARY OF

ARGUMENT ......................................................... 2

ARGUMENT................................................................ 5

I.

Undue hardship requires a context-specific

inquiry that, contrary to the Fifth Circuit’s

view, may depend on individualized

evidence about employees. .................................... 5

A. As Groff explained, undue hardship is a

“fact-specific inquiry” tailored to the

“context” of each employee’s

circumstances. ................................................ 6

B. By considering only Respondents’

evidence, the Fifth Circuit incorrectly

concluded that undue hardship poses a

single question across all employees at

all airports. ..................................................... 8

II. Diversity across the industry—including

among airports, CBA protections, and state

laws—makes airlines’ undue-hardship

defenses inherently individualized. ................... 10

A. Dramatic differences in space,

resources, and staffing among airports

make company-wide accommodations

substantially burdensome. ........................... 11

ii

TABLE OF CONTENTS

(continued)

Page

B. Accommodating flightcrew poses risks

of violating CBAs and federal law,

which vary in application to different

employees and which alone impose an

undue hardship. ............................................ 13

C. Interstate and international flights

require confronting different state and

foreign laws and thus require

individualized inquiries. .............................. 18

III. The Fifth Circuit’s sua sponte alternative

accommodations to masking-and-testing

pose even more individualized questions. .......... 19

A. A quarantine requirement would have

posed an undue hardship for most, but

perhaps not all, employees. .......................... 20

B. Unvaccinated-only flightcrews would be

feasible, if at all, for only a limited

subset of routes in well-resourced

airports. ......................................................... 23

CONCLUSION .......................................................... 26

iii

TABLE OF AUTHORITIES

Page(s)

CASES

Bernstein v. Virgin America, Inc.,

3 F.4th 1127 (9th Cir. 2021),

cert. denied, 142 S. Ct. 2903 (2022) ....................... 19

Castano v. American Tobacco Co.,

84 F.3d 734 (5th Cir. 1996) .................................... 18

City of Burbank v. Lockheed Air

Terminal, Inc.,

411 U.S. 624 (1973) ................................................ 19

Groff v. DeJoy,

600 U.S. 447 (2023) ......................................... 2, 3, 4,

..................................................................... 6, 7, 8, 9,

.............................................................. 10, 16, 17, 20

In re U.S. Foodservice Inc.

Pricing Litigation,

729 F.3d 108 (2d Cir. 2013) ................................... 18

Klay v. Humana, Inc.,

382 F.3d 1241 (11th Cir. 2004) .............................. 18

McDonnell Douglas Corp. v. Green,

411 U.S. 792 (1973) .................................................. 6

Speerly v. General Motors, LLC,

143 F.4th 306 (6th Cir. 2025)

(en banc) ............................................................... 6, 8

Trans World Airlines, Inc. v.

Hardison,

432 U.S. 63 (1977) ................................ 16, 17, 22, 23

Virginian Railway Co. v. System

Federation No. 40,

300 U.S. 515 (1937) ................................................ 15

iv

TABLE OF AUTHORITIES

(continued)

Page(s)

Wal-Mart Stores, Inc. v. Dukes,

564 U.S. 338 (2011) ......................................... 2, 4, 5,

........................................................................ 6, 8, 12

Yeager v. FirstEnergy Generation Corp.,

777 F.3d 362 (6th Cir. 2015)

(per curiam) ............................................................ 17

STATUTES

Rules Enabling Act,

28 U.S.C. § 2072(b) ................................................ 10

Title VII of the Civil Rights Act of 1964,

42 U.S.C. § 2000e et seq. ......................................... 1,

............................................................................. 2, 3,

..................................................................... 6, 10, 11,

.............................................................. 16, 17, 20, 25

42 U.S.C. § 2000e(j) ....................................... 2, 6, 17

42 U.S.C. § 2000e-2(h) ..................................... 22, 23

Railway Labor Act

45 U.S.C. § 152 Ninth ............................................ 15

49 U.S.C. § 41713(b)(1).............................................. 19

Cal. Lab. Code § 222.5 ............................................... 18

Va. Code Ann. § 40.1-28 ............................................ 18

REGULATIONS AND RULES

14 C.F.R. § 121.385 ................................................... 12

14 C.F.R. § 117.5(d) ................................................... 14

14 C.F.R. § 121.315(b) ............................................... 14

14 C.F.R. § 117.25(e) ................................................. 14

Ill. Admin. Code title 56, § 300.860 .......................... 18

v

TABLE OF AUTHORITIES

(continued)

Page(s)

Transport Canada, Interim Order Respecting

Certain Requirements for Civil Aviation

Due to COVID-19, No. 18 § 7(a)

(Jan. 7, 2021), https://tinyurl.com/

mumxmac6 ............................................................. 22

§ 10.3(1) ............................................................ 21, 22

Fed. R. Civ. P. 23 ................................................ 3, 4, 5,

.................................................................. 6, 8, 12, 25

Fed. R. Civ. P. 23(b)(3) ......................................... 2, 6

Fed. R. Civ. P. 23(c)(4) ........................................... 19

Fed. R. Civ. P. 23(c)(5) ........................................... 19

S. Ct. R. 37.2(a)............................................................ 1

S. Ct. R. 37.6 ................................................................ 1

OTHER AUTHORITIES

Departures, SRQ,

https://tinyurl.com/mnj7rrv8

(last visited Sept. 8, 2026) ..................................... 12

USPS, Annual Report to Congress (2025),

https://tinyurl.com/4hv9a8tb ................................... 9

1

INTERESTS OF AMICUS CURIAE

Founded in 1936, Airlines for America (A4A) is the

oldest and largest airline trade association in the

United States. A4A represents passenger and cargo

airlines nationwide, including Alaska Airlines, American Airlines, Atlas Air, Delta Air Lines, FedEx,

Hawaiian Airlines, JetBlue Airways, Southwest Airlines, United Airlines, and United Parcel Service.

Together, A4A’s members directly employ more than

80% of the airline industry’s 750,000 workers. And in

2020, A4A’s passenger carrier members and their

marketing partners carried more than 227 million

passengers—approximately 70% of the annual total—

and A4A’s all-cargo and passenger members together

carried 80% of U.S. airlines’ total cargo.*

A4A has a strong interest in this case. Many features of the airline industry, such as the diversity of

airport layouts and varying obligations under collective bargaining agreements (CBAs), require contextdependent analysis of requests for religious accommodations under Title VII of the Civil Rights Act of 1964,

42 U.S.C. § 2000e et seq., to balance the need for

meaningful accommodations for employees with the

need to avoid undue hardship for airlines. The decision below affirmed class certification on the notion,

among others, that one of A4A’s members, United Airlines, could have implemented a single religious

* Pursuant to this Court’s Rule 37.2(a), counsel for A4A no-

tified counsel of record for both parties of its intent to file this

brief on August 28, 2026, more than ten days before the deadline

for and filing of this brief. No party or counsel for a party authored this brief in whole or in part or made a monetary

contribution intended to fund the preparation or submission of

the brief. See Sup. Ct. R. 37.6.

2

accommodation nationwide based on a unitary religious-accommodation and undue-hardship inquiry.

That notion assumes, against this Court’s class-action

precedent, that the jury will adopt only the plaintiffs’

evidence; ignores the way the airline industry functions; and opens the door to class actions that, like this

one, raise a host of employee-specific issues that require individualized litigation.

INTRODUCTION AND

SUMMARY OF ARGUMENT

The Fifth Circuit’s endorsement of a companywide class of United pilots and flight attendants who

sought religious accommodations from United’s

Covid-19 vaccine requirement contravenes this

Court’s class-certification and Title VII precedents

and ignores the basic realities—practical, financial,

and logistical—about how the commercial aviation industry works. The Court should intervene before the

Fifth Circuit’s opinion does serious damage.

Class certification under Federal Rule of Civil

Procedure 23(b)(3) requires “common” questions that

“predominate over any questions affecting only individual members.” A question is “common” when the

“determination of its truth or falsity will resolve an issue that is central to the validity of each one of the

claims in one stroke.” Wal-Mart Stores, Inc. v. Dukes,

564 U.S. 338, 350 (2011).

The class certified here comes nowhere near this

high bar. Among many other individualized considerations, United is entitled to show that accommodating

an employee’s religious practice would impose “undue

hardship” on the airline. 42 U.S.C. § 2000e(j). In Groff

v. DeJoy, 600 U.S. 447, 468, 470, 473 (2023), the Court

clarified that “undue hardship” is a “fact-” and

3

“context-specific standard” dependent on “all relevant

factors in the case at hand, including the particular

accommodations at issue.” That’s the very opposite of

a common question.

But the Fifth Circuit blew past that. It reasoned

that the undue-hardship standard can be applied on a

classwide basis because it’s possible a jury could agree

with plaintiffs’ account that the burden of alternative

accommodations could be uniform across United’s

workforce. See Pet. App. 30a.

That sweeping generalization misunderstands

both Groff and Rule 23 commonality and predominance. It also threatens to wreak havoc across

airlines. Accommodating religious practice requires

individualized consideration of, among other variables, each employee’s airports and routes as well as

any applicable CBAs, federal regulations, and state

laws. To be clear, the Court need not decide whether

United or the plaintiffs are right about if, for any individual employee’s accommodation, the burden on

United rises to the level of undue hardship. Rather, it

need only reaffirm that the undue-hardship inquiry

can vary from employee to employee. Groff didn’t eliminate individualized considerations from the unduehardship inquiry, and Rule 23 doesn’t permit certification in spite of them. Holding otherwise exposes

airlines to a flurry of class actions, in Title VII and

beyond, riddled with individualized questions.

1. As Groff explains, “‘undue hardship’ is shown

when a burden is substantial in the overall context of

an employer’s business.” 600 U.S. at 468. The Fifth

Circuit reasoned that undue-hardship question is answerable classwide because it “does not require

United to submit employee-specific evidence.” Pet.

4

App. 29a-30a. But “does not require” and “does not allow” are two different things. Groff requires a “fact-”

and “context-specific” undue-hardship assessment of

“all relevant factors” for “the particular accommodations at issue.” 600 U.S. at 468, 470-72. That means

United is entitled to submit fact-specific evidence for

each employee. And as the record shows, United has

submitted and will continue to submit volumes of employee-specific evidence. Its undue-hardship defenses

are impossible to resolve “in one stroke.” Wal-Mart,

564 U.S. at 350.

2. The Fifth Circuit’s misunderstanding of Rule

23 and Groff poses special problems for the airline industry. Given the great variation across airports, CBA

protections, and state laws, company-wide accommodations raise a host of individualized issues.

Consider airports. For any given airline at any

given airport, there are unique limits to making accommodations based on the space, equipment, and

staffing available. What can be accomplished using,

say, United’s extensive floorspace and staffing at

Washington Dulles International Airport might be

next to impossible at the Sarasota Bradenton International Airport.

CBAs throw another wrench in the works. Many

of their provisions, especially when paired with federal safety regulations, restrict airlines’ flexibility to

change employees’ routes and duties. And breaching a

CBA or federal law, without more, is undue hardship.

The interstate and international nature of most

air travel creates yet another complication. States frequently try to apply their varying employment laws to

flightcrew. Those varying laws—including whether

they survive federal preemption—create further

5

employee-by-employee variation in airlines’ ability to

make accommodations.

3. Every alternative to United’s vaccine requirement implicates these airline-inherent individualized

considerations. As to “masking-and-testing,” for instance, limitations posed by airport characteristics

and CBA requirements alike would often make it substantially burdensome for United to require regular

testing and respond accordingly whenever an unvaccinated employee tests positive. But the key point here

is that the inquiry isn’t the same classwide.

The Fifth Circuit offered two alternative accommodations sua sponte, see Pet. App. 30a n.9, but they

fare no better. Regarding an unspecified “quarantine

requirement,” id., United couldn’t quarantine unvaccinated employees without knowing every passenger’s

Covid-19 status, which would have been unobtainable

on most, but perhaps not all, flights. And regarding

“unvaccinated-only flight crew,” id., that proposal too

disregards the reality of airports and CBAs. The bottom line is that these proposals cannot be evaluated

classwide, either.

The Court should grant the petition.

ARGUMENT

I.

Undue hardship requires a context-specific

inquiry that, contrary to the Fifth Circuit’s

view, may depend on individualized

evidence about employees.

Under Rule 23, class certification requires “questions of law or fact common to the class.” As this Court

has emphasized, a question is “common” only if the

“determination of its truth or falsity will resolve an issue that is central to the validity of each one of the

6

claims in one stroke.” Wal-Mart, 564 U.S. at 350. Put

differently, “[i]f a reasonable decisionmaker left with

the evidence may answer ‘yes’ to a question for some

class members and ‘no’ for others, the class has not

shown that it is common.” Speerly v. General Motors,

LLC, 143 F.4th 306, 316 (6th Cir. 2025) (en banc).

What’s more, as relevant here, those common questions must “predominate over any questions affecting

only individual members.” Fed. R. Civ. P. 23(b)(3).

Title VII lawsuits, and particularly religious-accommodation claims, don’t easily satisfy this rigorous

standard. As the Court has recognized, “[t]he facts

necessarily will vary in Title VII cases.” McDonnell

Douglas Corp. v. Green, 411 U.S. 792, 802 n.13 (1973).

Among other individualized elements, see Pet. 18-23,

employers can raise a “fact-specific” defense, Groff,

600 U.S. at 468, that will almost invariably fail to

meet Rule 23’s commonality and predominance requirements: undue hardship.

A. As Groff explained, undue hardship is a

“fact-specific inquiry” tailored to the

“context”

of

each

employee’s

circumstances.

Title VII doesn’t require an employer to accommodate an employee’s religious practice if doing so would

impose an “undue hardship on the conduct of the employer’s business.” 42 U.S.C. § 2000e(j). As this Court

clarified in Groff, “‘undue hardship’ is shown when a

burden is substantial in the overall context of an employer’s business.” 600 U.S. at 468. This showing

“takes into account all relevant factors in the case at

hand, including the particular accommodations at issue and their practical impact in light of the nature,

7

size, and operating cost of [an] employer.” Id. at 47071 (alteration in original).

1. Such a “fact-specific inquiry,” id. at 468, necessitates a host of individualized considerations. For

example, where does the employee work? Does that location have staffing and resources to accommodate

him, or would he need to be redeployed elsewhere?

And are there any jurisdiction-specific laws or arrangements with contractual service providers that

might cause some accommodations to be costlier for

the employer than others?

Consider too how the accommodations process often varies by position. Can the employee work other

jobs within the business without needing to, say, take

time off for retraining? What if there’s a CBA? Does it

limit the employer’s ability to redeploy employees

such that otherwise reasonable accommodations are

unavailable?

2. As explained below (at 10-19), analyzing those

questions and others for all members of the class that

the Fifth Circuit endorsed will require answers tailored to each employee based on his location, seniority,

and other non-classwide factors. Regardless of

whether some employees seek the same type of accommodations, the burden of making that accommodation

isn’t the same for all of them. The “practical impact”

of a “particular accommodation[]” varies from person

to person. Groff, 600 U.S. at 470.

8

B. By considering only Respondents’

evidence, the Fifth Circuit incorrectly

concluded that undue hardship poses a

single question across all employees at

all airports.

The Fifth Circuit affirmed class certification

based on a misunderstanding of Rule 23 and Groff. According to the court, the question of “an undue burden

can be answered class-wide” without “requir[ing]

United to submit employee-specific evidence” because

the airline must prove that any alternative to masking-and-testing “would have imposed a burden that is

‘substantial in the overall context of [United’s] business.’” Pet. App. 29a-30a (quoting Groff, 600 U.S. at

468; second alteration in original). That was error.

1. Just because a question can be answered

classwide with common evidence doesn’t mean it satisfies Rule 23’s commonality and predominance

requirements. To reiterate, commonality exists only

when a question must be answered across the entire

class “in one stroke.” Wal-Mart, 564 U.S. at 350. Considering the countless individualized questions that

could produce different answers for different employees, it’s nearly certain that “a reasonable

decisionmaker left with the evidence” will “answer

‘yes’ to a question for some class members and ‘no’ for

others.” Speerly, 143 F.4th at 316.

2. The Fifth Circuit also ignored how undue

hardship is a “fact-specific inquiry.” Groff, 600 U.S. at

468. An accommodation poses an undue hardship if—

in the context of the employee’s relationship to the

greater business—the burden is substantial. But rather than take this “common-sense” approach, id. at

471, the Fifth Circuit viewed Groff’s undue-hardship

9

analysis to require weighing the burden of an accommodation in a vacuum against the employer’s entire

business, without consideration of each employee’s

circumstances. See Pet. App. 29a-30a. Respondents

make that erroneous view even more explicit, claiming “[t]he factors [Groff] identified … apply companywide and do not vary from one class member to another.” Opp. 29.

That view is incompatible with this Court’s command that undue hardship is “context-specific.” Groff,

600 U.S. at 473. Indeed, preventing employers from

showing hardship specific to a plaintiff’s circumstances would effectively eliminate undue hardship as

a defense for large employers whenever a plaintiff

sues individually. Consider the facts of Groff itself.

There, an individual sued the United States Postal

Service (USPS), id. at 456, which has over 620,000 employees, see USPS, Annual Report to Congress 3

(2025), https://tinyurl.com/4hv9a8tb. It’s hard to imagine how a religious accommodation for any single

employee could ever impose a substantial burden on

the USPS without consideration of the specific context.

Of course, Groff doesn’t support such an absurd

approach. If it did, the Court wouldn’t have remanded

while leaving open “the possibility that the USPS will

prevail” in showing undue hardship depending on the

application of this “context-specific standard.” Groff,

600 U.S. at 473. That standard requires assessing the

“practical impact,” given the employer’s “nature, ‘size

and operating cost,’” id. at 470-71, of accommodating

a particular employee and what it would mean for accommodating similarly situated employees, since

employers cannot treat similarly situated employees

differently without a legitimate justification. At the

10

same time, not all employees seeking religious accommodations are similarly situated. Thus, Groff clarified

that courts must perform a “fact-specific inquiry” to

determine whether an accommodation poses a substantial burden. Id. at 468.

And that inquiry turns on each employee’s circumstances. Here, United can make different unduehardship defenses for different employees based on

their circumstances, and those defenses do not necessarily rise or fall together. A court cannot inject

commonality simply by aggregating the burdens of

every plaintiff’s proposed accommodations—whether

or not they are substantial standing alone—to make

one overarching undue-hardship determination that

everyone must live by. Doing so would violate the prohibition against “enlarg[ing] … substantive right[s]”

in the Rules Enabling Act. 28 U.S.C. § 2072(b).

II. Diversity across the industry—including

among airports, CBA protections, and state

laws—makes

airlines’

undue-hardship

defenses inherently individualized.

The undue-hardship inquiry is inherently individualized in the commercial aviation setting. Airports

differ considerably in space and staffing, meaning

that an accommodation that is frictionless at one airport could pose an undue hardship at another.

Airlines are also typically subject to multiple CBAs

across their workforces, and those CBAs limit their

flexibility to change employees’ duties to implement

accommodations without significant consequences.

And the interstate or international nature of most

flights means that (absent federal preemption) airlines must confront varying state laws, particularly

those about public health. Given all this

11

heterogeneity, airlines cannot make a single, sweeping accommodation under Title VII that covers every

employee nationwide who seeks the same type of religious exemption. Their hardship of accommodating

different employees will necessarily vary, and could

produce different results under Title VII.

A. Dramatic differences in space, resources,

and staffing among airports make

company-wide

accommodations

substantially burdensome.

No two airports are the same. Rather, each has

unique parameters regarding space, equipment, and

staff available to any given airline. That variability

means airlines will be required to tailor their accommodations for employees to each airport’s capabilities.

1. Differences among airports are particularly

pronounced for the many airlines, such as United,

that follow a hub-and-spoke system. By design, the

system produces different footprints from airport to

airport. As the focal point for all other flights, hubs

demand more gates, equipment, and staff than

spokes. CA5.ROA.7954. For example, United occupies

roughly 80% of the floorspace at Washington Dulles

International Airport, one of its hubs, but less than

20% of the floorspace at Ronald Reagan Washington

National Airport, one of its spokes. CA5.ROA.7494.

These variations mean that the tools available to

accommodate a Title VII claimant will often depend

on the employee’s location. An airline’s hubs may have

enough space, equipment, and staffing to make an accommodation viable even if that same accommodation

would impose an undue hardship at less-resourced

airports. There is no one-size-fits-all solution.

12

2. Consider the proposed accommodation that

captured the Fifth Circuit’s focus: a masking-and-testing requirement where unvaccinated employees could

continue working for United so long as they wore

masks and regularly submitted Covid-19 test results.

According to the court, the burden of that accommodation “can be answered class-wide.” Pet. App. 29a.

But again, that doesn’t mean it must be answered

classwide—the relevant inquiry under Rule 23. See

Wal-Mart, 564 U.S. at 350. At its hubs, United might

have enough resources to equip unvaccinated employees with masks and tests, as well as have backup staff

in case one of those employees tests positive. At

smaller airports, however, clearly neither of those approaches is feasible. Take the Sarasota Bradenton

International Airport. Most days, just a few United

flights depart from it. See Departures, SRQ, https://tinyurl.com/mnj7rrv8 (last visited Sept. 8, 2026). So,

the airport only needs a thin staff to serve United’s

passengers.

Masking-and-testing could have made the situation untenable. For example, what would have

happened when an unvaccinated pilot tested positive

for Covid-19? United doesn’t keep reserve crew at Sarasota Bradenton, and federal law prohibits it from

running flights short-staffed. See 14 C.F.R. § 121.385.

So the only options would have been cancelling the

flight (likely causing cascading cancellations, see

CA5.ROA.2120)—and lose ticket sales—or keeping

extra staff at the airport—and massively increase labor costs, likely to the point of making the flights

uneconomical, see CA5.ROA.1676, 8304. Either option

could have resulted in serious reputational damage in

addition to customers’ loss of services. Masking-andtesting could therefore have imposed an undue

13

hardship at those airports—and could have done so

based on considerations that likely would not apply at

larger airports and to other employees. The different

pieces of evidence, and the answers they produce, thus

could vary across the class, meaning there shouldn’t

be one in the first place.

B. Accommodating flightcrew poses risks of

violating CBAs and federal law, which

vary

in

application

to

different

employees and which alone impose an

undue hardship.

Many airline employees are unionized and thus

work under collective-bargaining agreements, which

set terms that employees and airlines must honor.

The vast majority of United’s customer-facing employees are represented by one of three unions: the Air

Line Pilots Association, International; the Association

of Flight Attendants; and the International Association of Machinists (covering customer-service

representatives, like gate agents). CA5.ROA.1671,

2115, 2705. Each union has a separate CBA with

United. See CA5.ROA.1679-2112, 2124-701, 2708-840.

And each of those CBAs raises multiple individualized

complications, both under its own terms and through

its interaction with federal regulations, because violating a CBA or federal law necessarily imposes undue

hardship.

1. Start with masking-and-testing. That approach would be impossible for many flight

attendants—yet would still require an employee-byemployee assessment—based on the CBA and the respective flight attendant’s assignments.

To explain: United’s CBA with flight attendants

prohibits it from changing the scheduled times at

14

which they must report to the airport when they are

flying on certain aircraft. CA5.ROA.1729. And because they already have a host of pre-flight duties

(often required by federal regulation, see, e.g., 14

C.F.R. §§ 117.5(d), 121.315(b)), many flight attendants wouldn’t have enough time to test and wait for

their results before coming into contact with other

people. For those flight attendants, United couldn’t

implement masking-and-testing without breaching

the CBA, the law, or both.

At the same time, a reasonable factfinder might

determine that it was feasible for some employees to

have tested at the start of each workday, because the

check-in-time requirements can vary by aircraft.

CA5.ROA.1658, 1729. And pilots, while subject to

their own start-of-shift duties, see CA5.ROA.2118-19,

don’t have the same hard-and-fast CBA-based limits.

Respondents argued below (CA5.ROA.1654) that

United could have resolved those concerns simply by

requiring employees to test themselves on their own

time. But that would likewise have risked running

afoul of the CBAs and federal law, which both require

United to give pilots and flight attendants sufficient

uninterrupted periods of rest between work-related

functions. CA5.ROA.1732-34, 2198-99, 2213-15; 14

C.F.R. § 117.25(e).

Because company-mandated medical testing may

count as time on duty, CA5.ROA.1654, 1673, 2117,

United could have needed to give employees uninterrupted periods of rest before and after at-home

testing. But for some employees, that wouldn’t be possible. In particular, pilots and flight attendants whose

scheduled rest periods are already at the minimum

15

(under federal law or their respective CBA) wouldn’t

have enough time to fit testing into their schedule.

Consider too that United’s flightcrew CBAs guarantee a certain number of completely off-duty days.

CA5.ROA.1728, 2199-203, 2215-16, 2346. If a testing

policy required an employee to test on those days,

those days may no longer qualify as “off.”

CA5.ROA.1676, 2120. So for those flightcrew already

near the minimum number of off-duty days, the Fifth

Circuit’s proposed accommodation risks violating

their rights under the CBAs, too.

2. Respondents argued below (CA5.ROA.1662)

that accommodation-seeking employees could have

just “waived” CBA provisions that would have imposed an undue hardship on United. But that

approach likewise would have presented serious concerns, because the Railway Labor Act (which applies

to airlines) “imposes the affirmative duty to treat only

with the true representative, and hence the negative

duty to treat with no other.” Virginian Railway Co. v.

System Federation No. 40, 300 U.S. 515, 548 (1937);

see 45 U.S.C. § 152 Ninth. If only the authorized union

representative could agree to alter or waive CBA protections, it is unclear how employees and United could

have agreed on the necessary waivers.

Indeed, the union representatives here stated that

they wouldn’t have agreed to waivers that adversely

affect

other

employees’

contractual

rights.

CA5.ROA.2114, 2703. That’s a problem for Respondents because the waiver of a CBA provision for one

employee (assuming that selective waiver is lawful)

can frequently infringe on other employees’ CBA

rights. For example, to promote fairness and verify attendance, the flight attendant CBA requires that any

16

changes to one attendant’s check-in time apply to

every attendant scheduled for the same set of trips.

CA5.ROA.1729. Expanding the check-in time to accommodate testing would therefore require

vaccinated attendants to arrive earlier to work, too.

3. The concerns laid out above are just a few examples of the CBA-related problems with the notion

that accommodations and undue hardship can be determined by classwide evidence. When a workforce

has extensive union representation, as is true for

many airlines, company-wide accommodations would

often run afoul of CBA protections for some—but not

all—employees. That matters here because breaching

a CBA itself amounts to an undue hardship, no matter

the impact to the employer’s bottom line.

This Court recognized—in the aviation setting—

that CBA violations impose undue hardship. In Trans

World Airlines, Inc. v. Hardison, 432 U.S. 63, 66-69

(1977), an aircraft-parts clerk requested time off of

work to observe the Sabbath. The Court held that the

employer’s inability to accommodate him didn’t violate Title VII because permitting his requested

absence would have “deprived” more senior employees

of their “contractual rights under the[ir] collectivebargaining agreement” to have priority when bidding

for shifts. Id. at 80. The Court held “that the duty to

accommodate” does not “require[] [the employer] to

take steps inconsistent with the otherwise valid

agreement.” Id. at 79.

Groff’s clarification of the undue-hardship test,

600 U.S. at 468, does not undermine Hardison’s holding that breaching a CBA amounts to an undue

hardship. Indeed, in Groff, the “continued vitality of

Hardison’s core holding on its ‘principal issue’”—

17

“seniority rights” in the CBA—was unchallenged. Id.

at 462 & n.10. And for good reason: Because undue

hardship under Title VII looks to “the conduct of the

employer’s business,” 42 U.S.C. § 2000e(j) (emphasis

added), it “may include undue hardship on the business’s employees,” such as by depriving them of their

CBA-guaranteed rights, Groff, 600 U.S. at 475 (Sotomayor, J., concurring). For that same reason, the

breaches of the CBAs that some plaintiffs demand

here would have amounted to an undue hardship.

4. The same goes for proposed accommodations

that require an employer to break the law. “Every circuit to consider the issue has” reached “the same,

sensible conclusion: ‘[A]n employer is not liable under

Title VII when accommodating an employee’s religious beliefs would require the employer to violate

federal … law.’” Yeager v. FirstEnergy Generation

Corp., 777 F.3d 362, 363 (6th Cir. 2015) (per curiam)

(alterations in original).

That’s a critical problem for class certification

here. As discussed above, employees’ rights under airlines’ CBAs often intersect with federal regulations to

doubly prohibit changing the terms of employment for

flightcrew. The Federal Aviation Administration imposes strict duties on pilots and flight attendants,

while those employees’ CBAs guarantee them various

protections. The result is that airlines have little flexibility to make accommodations for many employees,

and making that determination on a classwide basis

is impossible.

18

C. Interstate and international flights

require confronting different state and

foreign

laws

and

thus

require

individualized inquiries.

Most major airline flights, including United’s,

cross state or international borders. That routine

business exposes airlines to a complex web of different

jurisdictions’ laws, which can often vary or even conflict. Here, those varying laws require yet another set

of individualized inquiries.

1. Some states purport to require employers to

pay for any medical examinations, including Covid-19

tests, that are a condition of employment. See, e.g.,

Cal. Lab. Code § 222.5; Ill. Admin. Code title 56,

§ 300.860; Va. Code Ann. § 40.1-28. At the time of

United’s vaccine mandate, each Covid-19 test cost the

airline around $97. CA5.ROA.1079. Incurring that expense for unvaccinated employees every week (if not

every day) could well pose an undue hardship. Other

states don’t require employers to pay for Covid-19

tests, but instead allow expenses to be split with employees. That difference could produce a different

result as to undue hardship.

2. The tension between state law and commonality is no surprise. Many courts—including the Fifth

Circuit—have recognized that “[i]n a multi-state class

action, variations in state law may swamp any common issues and defeat predominance.” Castano v.

American Tobacco Co., 84 F.3d 734, 741 (5th Cir.

1996); accord, e.g., In re U.S. Foodservice Inc. Pricing

Litigation, 729 F.3d 108, 127 (2d Cir. 2013); Klay v.

Humana, Inc., 382 F.3d 1241, 1261 (11th Cir. 2004).

To be sure, the fact that a class action involves different state laws doesn’t necessarily defeat

19

commonality. And courts have several tools for making class actions with varying state issues more

manageable, such as by limiting the action “to particular issues” or “divid[ing]” the class “into subclasses.”

Fed. R. Civ. P. 23(c)(4)-(5). But neither the Fifth Circuit nor the district court tried using them to mitigate

the potential state- or foreign-law complications.

3. Of course, state and local laws are often

preempted in the commercial-aviation context. See,

e.g., 49 U.S.C. § 41713(b)(1); City of Burbank v. Lockheed Air Terminal, Inc., 411 U.S. 624, 633 (1973). But

courts nonetheless sometimes require application of

those laws even when they should not. See, e.g., Bernstein v. Virgin America, Inc., 3 F.4th 1127, 1138-41

(9th Cir. 2021) (rejecting several theories of preemption regarding the imposition of state meal-and-restbreak laws on airlines), cert. denied, 142 S. Ct. 2903

(2022); see also U.S. CVSG Br. 10-17 (No. 21-260) (explaining at length how the Ninth Circuit’s preemption

reasoning “was misguided”). Regardless, preemption

questions themselves raise different questions depending on different jurisdictions’ laws, and thus only

compound, not eliminate, the lack-of-commonalityand-predominance problem with trying to certify a

class to assess company-wide accommodations.

III. The Fifth Circuit’s sua sponte alternative

accommodations to masking-and-testing

pose even more individualized questions.

The Fifth Circuit spent most of its attention addressing the burden posed by a masking-and-testing

policy. See Pet. App. 29a-30a. But in a footnote, the

court offered two other accommodations that it

thought could be assessed on a classwide basis: “a

quarantine requirement or the creation of an

20

unvaccinated-only flight crew for customers not apprehensive of the virus.” Pet. App. 30a n.9. Although

the court offered those proposals without any briefing

from the parties, it faulted United for failing to mention them, charging the airline with violating Title

VII’s obligation to “[c]onsider[] … other options” for

accommodations. Groff, 600 U.S. at 473; see Pet.

App. 29a & 30a n.9.

In reality, United considered but had to reject

many other options, including expanding sick leave to

allow absences whenever an employee reports a symptom of Covid-19, and allowing unvaccinated

employees with natural immunity from a prior Covid19 infection to return to work. See CA5.ROA.1660-61.

Not preemptively discussing the Fifth Circuit’s two

proposals in its briefs doesn’t reflect any failure on

United’s part to “consider[] … other options.” It

simply reflects how many individualized problems the

Fifth Circuit’s proposals created such that they didn’t

warrant discussion at this procedural stage in the first

place.

A. A quarantine requirement would have

posed an undue hardship for most, but

perhaps not all, employees.

Start with the quarantine requirement. While the

Fifth Circuit didn’t explain its thinking, its proposal

presumably refers to a policy where unvaccinated employees would have been required to refrain from

working for a specified period if they tested positive

for Covid-19 or were exposed to another person with

Covid-19. Either approach raises a host of individualized questions.

1. For starters, if the proposal would have required unvaccinated employees to test for Covid-19 at

21

regular intervals, it runs into the same set of individualized questions as the masking-and-testing policy

discussed above. See supra pp. 10-19.

2. Without regular testing, a quarantine requirement would presumably depend on “contact tracing,”

which would have required United to monitor whether

unvaccinated employees had been exposed to anyone

with Covid-19. If an employee was exposed, he would

then have needed to take leave until he could confirm

either that he hadn’t contracted Covid-19 or that he

had contracted the virus and had since recovered.

a. For many routes, that proposal would have

been a nonstarter. On a typical workday, flightcrew

interact with hundreds of passengers for hours at a

time and in tightly confined spaces. CA5.ROA.365. If

any of those passengers have the virus, they risk

spreading it to employees. To implement any effective

form of contact tracing, then, an airline would have

needed to determine the Covid-19 status of every passenger on every flight carrying unvaccinated

employees.

But that information is costly, if not impossible,

for airlines to obtain. Many passengers would balk at

an airline’s requiring them to submit a Covid-19 test

result before every flight, just as non-customer-facing

United employees balked at the testing requirement

in this case. See, e.g., CA5.ROA.5857. And an airline

couldn’t simply rely on passengers’ attestations to being free from Covid-19, because those responses risk

inaccuracies from, for instance, asymptomatic individuals who haven’t recently tested for the virus.

True, at the time of United’s vaccine mandate,

some countries required that all inbound travelers

show proof of a negative Covid-19 test result. See, e.g.,

22

Transport Canada, Interim Order Respecting Certain

Requirements for Civil Aviation Due to COVID-19,

No. 18 § 10.3(1) (Jan. 7, 2021), https://tinyurl.com/mu

mxmac6. But governments wield far greater power to

enforce public health protocols than companies. Most

notably, prospective customers frustrated by a testing

requirement could almost always change to an airline

that doesn’t require test results, imposing undue

hardship from the loss of business whenever such an

airline is available and a substantial number of passengers switch. By contrast, those same people cannot

readily make such a switch regarding their country of

residence.

b. Assuming the Fifth Circuit was right that a

quarantine requirement might have been feasible for

certain routes, that only underscores the lack of commonality and why a classwide answer to

accommodations or undue hardship isn’t guaranteed.

As just discussed, during the period of United’s vaccine mandate, numerous countries (including many

serviced by United) had adopted policies mandating

that all inbound passengers, but not flightcrew, on international flights provide documentation to their

airlines of a negative Covid-19 test result. See id.

§§ 7(a), 10.3(1).

But even if relieved of a requirement of tracking

passenger status, United couldn’t simply reassign all

unvaccinated employees to work on only flights entering countries with negative-test-result policies.

Flightcrew CBAs set forth strict rules around the bidding process for routes, prioritizing individual

characteristics like seniority. E.g., CA5.ROA.1740,

2343. And as explained above (at 13-17), breaching a

CBA (including, specifically, seniority rights therein)

23

itself constitutes an undue hardship. Hardison, 432

U.S. at 77; see also 42 U.S.C. § 2000e-2(h).

c. All of that means the Fifth Circuit’s quarantine requirement would require yet another set of

individualized inquiries making the case unsuitable

for classwide resolution. For flights where passengers

wouldn’t have needed to show proof of a negative

Covid-19 test result (such as all domestic travel in the

United States), contact-tracing would have been next

to impossible. For flights where different jurisdictions’

laws required provision of the information, tracing

might have not been substantially burdensome.

B. Unvaccinated-only flightcrews would be

feasible, if at all, for only a limited subset

of routes in well-resourced airports.

Equally unavailing is the Fifth Circuit’s suggestion that United could have offered class members

routes staffed by unvaccinated-only flightcrew. Aside

from perhaps senior employees at United’s busiest

and most spacious airports, a reasonable factfinder

couldn’t possibly find that accommodation to impose

an acceptable burden on the airline.

1. Recall that variations between airports make

any company-wide masking-and-testing policy unworkable. See supra pp. 11-13. The same reasoning

applies with even greater force to trying to maintain

an unvaccinated-only flightcrew.

At smaller airports where United retains a comparatively thin workforce, there wouldn’t have been

enough unvaccinated-only employees to staff entire

flights. Indeed, there often wouldn’t have been enough

demand from customers “not apprehensive of the virus,” Pet. App. 30a n.9, for another flight offering in

the first place. For these airports, then, United would

24

have needed to determine, among other things, that

the demand for additional unvaccinated-only flights

would justify allocating the necessary unvaccinated

flightcrew to service them. The likely result would be

needing to stop servicing the airport altogether.

Many airports also don’t have enough space and

equipment to sufficiently separate unvaccinated employees from vaccinated employees, let alone the

public. For example, employees on different flights

regularly come near one another during security

screening, which is often adjacent to the screening for

passengers. So except for airports with ample space

and equipment and numerous security agents to

maintain an isolated security checkpoint for unvaccinated flightcrew, those employees would still risk

spreading Covid-19 to numerous people who are apprehensive of the virus.

2. The Fifth Circuit likely conjured up its unvaccinated-only-flightcrew suggestion based on the

incorrect premise that United could have reassigned

unvaccinated employees to airports with sufficient

staffing and to routes with sufficient demand. But as

with the quarantine requirement, that approach

would have disturbed the comprehensive senioritybased bidding system for routes set forth in United’s

CBAs with pilots and flight attendants. See, e.g.,

CA5.ROA.1740, 2343. Thus, the approach likely

would have worked, if at all, for only senior employees

willing to work only in large, well-equipped airports

and only on routes with sufficient demand for flights

staffed by unvaccinated workers. Such a specific set of

qualifications cannot possibly come close to describing

the entire class.

25

*

*

*

While the Fifth Circuit applied its errant commonality reasoning in the Title VII setting, unless this

Court intervenes, that reasoning likely will spill over

into many other areas of class-action litigation affecting airlines (and other companies, too). Consumer

protection, Employee Retirement Income Security

Act, antidiscrimination, and other claims will often involve some amount of classwide evidence that

passengers or employees can point to. But if that were

enough for Rule 23, “no putative class would ever fail

the commonality requirement.” Pet. App. 44a (Willett,

J., concurring).

26

CONCLUSION

The Court should grant the petition for a writ of

certiorari.

Respectfully submitted.

Shay Dvoretzky

Counsel of Record

Parker Rider-Longmaid

Alexander M. Johnson

Alisha Nanda

SKADDEN, ARPS, SLATE,

Emily Jennings

MEAGHER & FLOM LLP

SKADDEN, ARPS, SLATE, 1440 New York Ave. NW

MEAGHER & FLOM LLP Washington, DC 20005

500 Boylston St.

202-371-7000

shay.dvoretzky@skadden.com

Boston, MA 02116

Douglas Mullen

Riva Parker

AIRLINES FOR AMERICA

1275 Pennsylvania

Ave. NW

Washington, DC 20004

Raza Rasheed

SKADDEN, ARPS, SLATE,

MEAGHER & FLOM LLP

2000 Ave. of the Stars,

Ste. 200N

Los Angeles, CA 90067

Counsel for Amicus Curiae

September 9, 2026