Social media users have criticised United Airlines after two girls were not allowed on a flight because they were wearing leggings.
Activist Shannon Watts tweeted about the incident and said the issue took place on Sunday morning (March 26) on a flight from Denver to Minneapolis, according to the BBC.
The pair were travelling using a special pass which has a dress code and is only available to employees and their guests.
Three other girls using the passes were also wearing leggings, but were allowed to fly as they put dresses over the top.
The dress code for those using the pass says passengers cannot wear "form-fitting lycra/spandex tops, pants and dresses" and should not expose their midriffs.
Mini skirts and flip-flops are also not allowed.
Watts criticised the rules and said: "This behaviour is sexist and sexualises young girls. Not to mention that the families were mortified and inconvenienced."
But in a statement about the incident, United Airlines said: "When taking advantage of this benefit, all employees and pass riders are considered representatives of United.
"And like most companies, we have a dress code that we ask employees and pass riders to follow."
Since the incident the airline has also clarified that all "regular" paying customers are entitled to wear leggings if they wish.