Teen girls in leggings told to cover up on United Airlines flight

United Airlines has found itself at the centre of a social media storm after it barred two girls from boarding a Denver to Minneapolis flight because they were wearing leggings.

Anti-gun violence advocate Shannon Watts began tweeting about the United gate agent who refused to allow the teens onto a flight because they were wearing the popular activewear garment.

Ms Watts, who witnessed the whole thing while waiting to board, shared her outrage with her more than 33,000 followers.

According to United, which responded in a series of curt tweets, the passengers were traveling with United Pass, a program for the company’s employees and approved travel companions, that requires travelers to follow an apparently strict dress code.

The dress code the company referenced, however, stated only that United reserves the right to refuse service to passengers who are “not properly clothed,” and that judgment is left up to the United agent.

Ms Watts pointed out that one of the young passengers appeared to be traveling with her father, who was dressed in shorts.

She noted that policies like this one — and so very many other dress codes — unfairly targeted women and girls, whose bodies and attire are inappropriately sexualized.

"She's forcing them to change or put dresses on over leggings or they can't board," she tweeted.

"Since when does @united police women's clothing?"

"A 10-year-old girl in gray leggings," she added of one of the girls. "She looked normal and appropriate."

• ‘Goodbye racist’: Passenger booted from plane after bomb accusation

• 'I’m going through a divorce': United Airlines pilot replaced after intercom rant to passengers

Another girl who was also wearing leggings was allowed to board the flight from Denver International Airport to Minneapolis after she changed, a witness said.

Twitter immediately exploded over the controversy.

One passenger tweeted that she was flying comfortably in leggings — on a Delta flight.

Even US model Christine Teigen chimed in, saying "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."

However, United Airlines maintained its support for the gate agent's decision in its own series of tweets.

Later, it clarified that the girls prevented from boarding were "pass riders" those who fly free or at heavily reduced rates because they are airline employees or their relatives.

The airline later clarified its dress code, stating " leggings are welcome" for regular customers.

"We care about the way we present ourselves to you, our customers, as we believe that is part of the experience on board our flights," the airline said in a statement.

"The passengers this morning were United pass riders and not in compliance with our dress code for company benefit travel. We regularly remind our employees that when they place a family member or friend on a flight for free as a standby passenger, they need to follow our dress code.

"To our regular customers, your leggings are welcome."