Wearing Leggings
This one is quite nonsensical and the airline that did this got a ton of bad press because of it. The entire Internet went up in a frenzy over it. In 2017 United Airlines refused to let two teen girls board a flight because they were wearing leggings.
A woman that saw the whole exchange put it up on Twitter, also noting that a man who was wearing shorts that stopped above the knee was allowed to board, asking “since when are airlines allowed to police what people wear”.
Later on, United said that since the girls were part of the “pass travelers” program, which lets family members of United employees fly for free, they had to adhere to a certain dress code different from other passengers.
This did not fly under the radar, as people claimed it was a poor excuse and United got a big blow to their reputation. So next time you want to be comfortable and are flying United, maybe change into some sweatpants, so you do not run the risk of not being allowed on the flight.