Olivia Culpo Forced By Airline To Cover Up In Christian McCaffrey's Hoodie

Olivia Culpo had to throw on her BF Christian McCaffrey's hoodie before her flight to Cabo ... and it wasn't due to cold weather -- it's because the airline told the 2012 Miss Universe she was showing too much skin.

OC's sister, Aurora, documented the whole debacle on Thursday ... showing Olivia in an all-black outfit with biker shorts, a crop top and a long cardigan.

Aurora says OC was called up to the front desk at their gate before boarding ... and one of the American Airlines workers told her she needed a blouse in order to get on the flight.

What's interesting -- the Culpo sisters point out another passenger who was also wearing a crop top, yet that lady wasn't told to cover up.

Luckily for Olivia, she didn't have to run to a nearby souvenir shop to fix the situation -- her NFL superstar boo offered up his comfy hoodie ... which led to a pretty cold and uncomfortable ride for him up in the air.

To make the whole situation even more inconvenient, the group's flight was delayed a bit ... but eventually, they made it up in the sky.