The headline pretty much tells the story here, doesn't it? Is this some hijacking (no pun intended) of the US Airways Twitter account by a rogue employee, or simply a fuck-up? (Very Not Safe For Work image below.)
@USAirways actually tweeted the photo out twice, and it's still there as of this writing. The photo was originally tweeted to American Airlines:
So what probably happened is some social media moron at US Airways tried to copy and paste the American Airlines tweet to a friend but instead tweeted it at some frustrated customers.
Update (3:27 p.m.): US Airways responds: