That’s a question women may be asking themselves before heading to the airport this summer, after news that a woman was barred from a flight over “inappropriate” shorts made national headlines.

On May 18, JetBlue employees stopped 26-year-old burlesque performer Maggie McMuffin from boarding a flight from Boston to Seattle, saying that her black-and-white-striped shorts might “offend other families on the flight.” McMuffin was only allowed on the plane after she changed into her last-minute airport store purchase: a $22 XL floral women’s pajama bottoms.

There’s been plenty of discussion of JetBlue’s decision online, with some people siding with the airline and others tweeting pro-McMuffin messages with hashtags like #BootyShortSupport.

But for all the outcry, this isn’t the first time an airline has deemed a woman’s outfit unfit for flight. Indeed, Southwest Airlines has been a serial offender. Back in 2007, the airline made headlines when a customer service supervisor escorted Kyla Ebbert off a flight from San Diego to Tuscan for an “inappropriate” ensemble consisting of a mini skirt, tank top, and cardigan. According to Jezebel, Southwest has also forced one woman to wear a blanket after a flight attendant deemed her top too low cut and requested that another woman button up her shirt to cover her cleavage before boarding.

So what gives Southwest, JetBlue, or any other airline the right to boot you off a flight? It comes down to the “contract of carriage,” a legal document that spells out the rights and responsibilities of the airline and its passengers. Whether you realize it or not, you agree to that contract whenever you purchase a ticket from an airline. In JetBlue’s case, it states that the airline can refuse “persons whose conduct is or has been known to be disorderly, abusive, offensive, threatening, intimidating violent, or whose clothing is lewd, obscene, or patently offensive.” Most other carriers use very similar language.

Adam G. Wasch, an attorney who has represented airlines in the past, says airlines’ contracts of carriage are “very enforceable.” The carriers tend to use broad language to give the discretion to the airline, he says, noting that the final call on whether someone is violating the terms often comes down to the captain of the flight. And because airlines “don’t want to get into the business of telling people what to wear or what not to wear,” says Wasch, they don’t give customers any guidance on what counts as “appropriate,” preferring to deal with clothing-related issues as they come up.

The problem here, of course, is that obscenity is in the eye of the beholder. And when it comes to women’s clothing, knowing whether a skirt is “too short” or a shirt “too low cut” is trickier than, say, realizing that a shirt with an obscenity printed on it might get you the boot. It seems clear that McMuffin’s shorts would have gone without comment on most flights—and if they were too short, how much longer would they have had to be to pass muster?

You’d think the airlines would be more specific. After all, we’re talking about an industry that knows a little something about short shorts. Just ask this Southwest flight attendant, circa 1972.