This article originally appeared on People.
United Airlines is facing major backlash after a woman tweeted that gate agents were not allowing young girls onto a flight because they were wearing leggings.
Shannon Watts, a mother-of-five from Colorado and founder of movement Moms Demand Action, shared her experience on a recent flight on Twitter, writing that the young passengers were forced to change before boarding a flight from Denver to Minneapolis.
“A @united gate agent isn’t letting girls in leggings get on flight from Denver to Minneapolis because spandex is not allowed?” she tweeted on Sunday. “She’s forcing them to change or put dresses on over leggings or they can’t board. Since when does @united police women’s clothing?”
Although some were allowed onto the plane after modifying or changing their outfits, she tweeted that two girls, one of whom was 10-years-old, were not allowed on the flight. Watts asked United for an explanation.
“They just boarded after being forced to change or put dresses on over the top of their clothing. Is this your policy?” Watts asked the airline.
United responded to Watts on Twitter, writing that they “have the right to refuse transport for passengers who are barefoot or not properly clothed.”
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While United does state this rule on their website, there is no details on what “properly clothed” implies.
“A 10-year-old girl in gray leggings. She looked normal and appropriate,” Watts responded. “Apparently @united is policing the clothing of women and girls.”
Many woman expressed their outrage at the situation while tweeting at the airline. In response to one tweet that defended wearing leggings for their comfort on flights, United doubled down on their action to remove the girls.
“United shall have the right to refuse passengers who are not properly clothed via our Contract of Carriage,” they wrote.
Furious Twitter users flooded United with responses, voicing their disagreement and confusion with the policy — and its lack of clear definition on what clothing is not acceptable.
“I’ve worn leggings on United flights dozens of times,” wrote one woman. “Very strange to enforce this rule randomly.”
Another user tweeted, “Define ‘properly clothed’ and how leggings don’t meet the standards of proper clothing, please.”
Later on Sunday, a United representative responded to Watts, saying that the people who were barred from traveling were “pass travelers” and have to follow a dress code when flying. Pass travelers is a term used for company employees and their family members who fly on discounted or comped tickets with their carrier.
United did not immediately respond to PEOPLE’s request for comment.