Spirit Airlines has revised its "contract of carriage" to include updated guidelines for passenger conduct and attire.

Spirit Airlines enforces a new dress code, banning transparent clothes and attire exposing private parts, in line with its updated contract of carriage.

Every airline has a contract of carriage, a legally binding document that flyers agree to abide by while doing business with the airline. These contracts contain language addressing passenger dress, though some are vague ― and very few travelers actually take the time to read them.