Young Thug Goes Off, Calling Airline Staff 'Nappy Peasants'

6:35 PM -- Young Thug's Seattle fans just got screwed ... he says he didn't make his backup flight, so he's postponing Wednesday night's show to Dec. 12.

Young Thug gave two female Alaska Airlines employees the business for trying to make him miss his flight and his show ... at least that's the way he saw it.

The rapper went in on the women pretty hard -- calling them "peasants" and "ants" with "nappy" hair. You can tell they're pissed as he tried to offer them $15k to quit their jobs.

A rep for the airline tells TMZ ... Thug was supposed to be on a flight from ATL to Seattle, but he arrived after their 45 minute cutoff period. We're told they still offered him a seat on a partner flight, but he declined..

It's unclear if he's going to make it in time for his 7 PM gig in Seattle.

We don't know what was said before Thug started recording, but the way he treats the women here ... makes him seem like a complete tool.