Now, once you know how to get through security, you need to know how to deal with your airline. Remember in 2017 when United Airlines turned away a group of leggings-clad girls for what was called "improper dress"? Would they really allow a clown-costumed traveler on board? Yes and no.
It turns out United's decision centered on the fact the girls were flying as "pass riders," and therefore representatives of the company. Restrictions for regular customers — including those dressed as ghouls or goblins — are much more lenient, as long as passengers follow the airline's carriage and safety guidelines.
Take Delta, for example. Its contract of carriage states it can "refuse to transport or may remove passengers from its aircraft ... when the passenger's conduct, attire, hygiene, or odor creates an unreasonable risk of offense or annoyance to other passengers." According to a representative, this includes Halloween costumes.
American Airlines has no specific restrictions when it comes to Halloween costumes, according to a representative; its conditions of carriage requires passengers to "be respectful that [their] odor isn't offensive" (unless caused by a disability), and notes that "bare feet or offensive clothing aren't allowed."
Contracts for United Airlines, JetBlue and Southwest Airlines all follow a similar tune. So that means as long as your costume isn't smelly or offensive, and doesn't cause injury to you or other passengers, you can fly in your favorite Halloween costume — although you may have a tougher time in business or first class. Attire rules tend to be more lax in economy.