The girls, one is 10 years old, were not allowed onto the morning flight because they were traveling under an employee travel pass that includes a dress code, United spokesman Jonathan Guerin said.
The dress code bars pass travelers from wearing spandex or Lycra pants such as leggings. The teenagers agreed to change their clothing and take a later flight, Guerin said, but the airline's actions sparked a quick backlash
Watts was traveling on vacation to Mexico when she heard a family next to her panic. Then she heard the female agent explain to the young travelers that they couldn’t get on the plane wearing spandex.
Watts said the girl's father was allowed to board while wearing shorts and called the airline's policy sexist.
And there you have it, the real story... schools aren't the only places with sexist dress codes.
http://www.kptv.com/story/35000594/teens-wearing-leggings-barred-from-united-flight
https://www.washingtonpost.com/news/dr-gridlock/wp/2017/03/26/two-girls-barred-from-united-flight-for-wearing-leggings/
Delta Air Lines saw the opportunity this presented... and was fast to say: "Flying Delta means comfort. (That means you can wear your leggings),"
http://fortune.com/2017/03/27/delta-united-leggings-ban/