United Airlines is in hot water with customers after a passenger flying the airline this morning observed and Tweeted about a group of tween girls who were denied boarding privileges on the airline for wearing an item many of us fly in on a daily basis: leggings.

Twitter user @shannonwatts (AKA the founder behind Moms Demand Action) caused a stir when she Tweeted the news that a gate agent forced the girls to either change or put dresses over their spandex bottoms.

United was quick to respond, telling Watts that in their 鈥渃ontract of carriage, Rule 21, we do have the right to refuse transport to passengers who鈥 are not 鈥減roperly clothed.鈥

Watts wasn鈥檛 having it, however, saying that the 10-year-olds in question looked 鈥渘ormal and appropriate.鈥

At least two famous faces, Patricia Arquette (who also called out the Oscars for their failing to include her trans sister in its memoriam segment) and Chrissy Teigen, were in complete agreement, and took to social media to say so:

United Airlines, for its part, is standing its ground, Tweeting that the passengers were 鈥減ass travelers鈥 (which means that they were free standby guests of United employees), and saying that the attire worn by the girls did not meet pass travel clothing requirements.

As a spokesman for the airline, Jonathan Guerin, told The New York Times 鈥淚t鈥檚 not that we want our standby travelers to come in wearing a suit and tie or that sort of thing,鈥 but such passengers are 鈥渞epresenting the company. We want people to be comfortable when they travel as long as its neat and in good taste for that environment.鈥

According to CNN Money, who spoke to another United employee, those requirements mandate that passengers refrain from wearing anything that doesn鈥檛 look 鈥渘eat and professional,鈥 including 鈥渇orm-fitting lycra or spandex tops, pants, and dresses.鈥

Watts pointed out the sexism of the company鈥檚 rules, telling the Times that the group鈥檚 patriarch wasn鈥檛 held to such high standards. 鈥淧lease keep in mind that the dad had on shorts that not hit his knee 鈥 they stopped maybe two or three inches above his knee 鈥 and there was no issue with that,鈥 she said.

The incident is reminiscent of a similar incident last summer, when JetBlue refused to let a woman board for wearing a pair of zebra shorts the airline deemed 鈥渋nappropriate.鈥 In that instance, while JetBlue initially defended its employee鈥檚 decision, the company was forced to apologize and issue credit after backlash grew over media attention.

We鈥檒l be curious to see if United soon follows suit.

What do you make of United鈥檚 #LeggingGate? Tell us over @BritandCo.

(h/t E!, photos via United Airlines/Getty)