It all kicked off on Sunday when two teenage girls, who were wearing leggings, were barred from boarding a United Airlines flight.

A company spokesperson said it was because they didn't meet a certain dress code put in place for special pass travellers.

If the girls had been paying customers, they would not have been refused entry on to the plane, the spokesperson added.

Shannon Watts, who was also travelling on the plane, overheard the conversation and she took to twitter to voice her disgust, "This behaviour is sexist and sexualises young girls. Not to mention that the families were mortified and inconvenienced."

The tweets led to thousands of women voicing their disappointment over United Airlines's decision to ban the girls from travelling, with celebrities getting involved in the conversation too.