BBC: The airline responded to a customer complaint with a pornographic image from its official Twitter account.
The image, which featured a naked woman and a toy plane, had originally been sent to the company's Twitter account by another user, it said.
It was then attached to a tweet that was sent to a US Airways customer who had taken to the social network to express her frustration that her flight was delayed.
Once the mistake had been realised US Airways deleted the offending tweet and issued an apology.
"We apologise for an inappropriate image recently shared as a link in one of our responses. We've removed the tweet and are investigating," it said on its Twitter feed.
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