Social Media Goes Nuts After United Airlines Bars Girls From Flight Over Leggings

United Airlines became the target of social media criticism Sunday after a gate agent in Denver reportedly barred girls from boarding a flight to Minneapolis because they were wearing leggings.

The brouhaha began with a string of tweets from Shannon Watts, founder of the anti-gun violence group Moms Demand Action, who has more than 30,000 Twitter followers.

According to her tweets, she saw a United gate agent refuse to let some girls on a plane unless they changed out of their athletic pants or put on a skirt.

In response, United Airlines said it had the right to refuse transport to people who are not "properly clothed," noting that the girls were pass riders, not regular airline customers.

In no time, the incident was trending on Twitter, with users both defending and attacking the company. Chrissy Teigen, Sarah Silverman -- even William Shatner chimed in — all critical of the airline.

The girls were able to board the flight after changing, according to Watts.