Rules for how airplane passengers should dress are often vague. Airline employees usually decide whether someone's clothing is offensive.
If you need guidance before heading to the airport, Google the airline's "contract of carriage" — the rules you agree to when buying a ticket — and look under "Acceptance of Passengers" or a similar-sounding section. Here are examples of clothing guidelines from the four biggest U.S. airlines:
— American Airlines: Bans passengers who "are clothed in a manner that would cause discomfort or offense to other passengers."
— Delta Air Lines: Reserves the right to remove passengers "for the comfort or safety of other passengers or Delta employees" or to prevent property damage.
— Southwest Airlines: Forbids passengers "whose clothing is lewd, obscene, or patently offensive."
— United Airlines: Bars anyone over 5 who is barefoot "or otherwise inappropriately clothed, unless required for medical reasons."