William Shatner, Patricia Arquette, Chrissy Teigen, Andy Richter and Sarah Silverman have slammed United Airlines after it barred two girls from boarding a flight wearing leggings.

Activist Shannon Watts of Denver, who claimed to have witnessed the incident, tweeted the young passengers boarding a flight from Denver to Minneapolis were told they could not board the plane unless they changed their outfits.

Watts also said one of the the girls' father was allowed to board while wearing shorts.

The airline's spokesman Jonathan Guerin said, "The girls were not allowed to board the plane from Denver to Minneapolis as they were travelling under an employee travel pass that includes a specific dress code."

Taking to Twitter, stars spoke out against the airline's confusing policy.

Arquette wrote in a series of tweets, "Why aren't you allowing girls to wear leggings on flights? Who is your gate agent policing girls clothing? Was there something strange about all these girls leggings?"

"Leggings are business attire for 10 year olds. Their business is being children. Why did dad board wearing shorts? Shorts are only business attire for Angus Young," she added.

Silverman tweeted, "Hey @united I fly a LOT. About to go on tour all April and changing all my @united flights to other airlines."

"@PattyArquette @Shananigans @united @shannonrwatts See.

I've done it before," Shatner posted alongside a picture of him standing shirtless.

Richter slammed the airline by writing, "I have flown numerous times while displaying an egregious moose knuckle.

What's a male over 10 have to do to get noticed?"

Teigen posted, "I have flown united before with literally no pants on. Just a top as a dress. Next time I will wear only jeans and a scarf."

United, however, responded to Watts, writing they "have the right to refuse transport for passengers who are barefoot or not properly clothed."

They later clarified that the girls in question were "pass travelers or travelers flying on comped or discounted tickets," typically reserved for employees and their family members.

United explained that they have a stricter dress code for pass travelers as they are representing the United brand