SYDNEY, July 27: A bomb threat found mid-flight on a United Airlines plane carrying 264 people forced an emergency return to Sydney on Tuesday, sparking a full alert in airspace in eastern Australia.

A government spokesman said the pilot of Los Angeles-bound flight UA840 decided to turn back 90 minutes into the journey after he was told of a note scrawled on a sickbag found in the toilets.

Transport Minister John Anderson said the note, found by a passenger, claimed there was a bomb onboard. The plane dumped excess fuel on the trip back to Sydney. Transport Minister John Anderson said the security scare resulted in a level three alert, the highest emergency rating in international aviation.

"It triggered the very real course of action right along the eastern seaboard and indeed airports across Australia as airspace was closed and everything from fire trucks and medical services were put on a very high level alert," he said. -Reuters