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.

The warning comes amid the introduction of a brand new set of travel restrictions, which disallows passengers donning 'lewd' and potentially-offensive clothing from flying. Spirit Airlines is a US-based budget airline headquartered in Miami, Florida, which operates scheduled flights across America, as well as the Caribbean and South America.