An 11-year-old girl asleep on a flight was horrified when she woke up to find a drunken man urinating on her leg, reports say.

The alleged incident occurred on a JetBlue flight between Portland and New York when a reportedly inebriated teenager stumbled out of his seat and began emptying his bladder on the sleeping child.

Associated Press reports angry scenes broke out on the flight when the girl’s father returned from the toilet and caught 18-yearo-old Robert Vietze in the act.

Flight attendants had to separate Vietze and the enraged father, witnesses told the media.

Vietze was arrested when the plane landed in New York but will not be charged, Associated Press reports.

"I was drunk, and I did not realise I was p***ing on her leg," Vietze said, according to authorities. He was questioned, issued summons and released.

A spokeswoman for JetBlue Airways Corp, based in Forest Hills, N Y, confirmed to Associated Press that an "incident" had taken place aboard the flight and that police had been called, but she declined to discuss it further.