A pilot arrested on suspicion of being over the alcohol limit has been cleared after tests found heavy dieting had caused his breath to smell like drink.
The flight was delayed as a substitute pilot was found
The Virgin Atlantic employee - held at Heathrow on 31 March before a flight to New York - had failed a breathalyser.
But samples taken from the 47-year-old prove his blood-alcohol level was consistent with a non-drinker.
Scientists say low-carbohydrate diets can produce acetone in the body, which may fool breath test equipment.
The long-serving pilot was said to have been on a heavy diet for a long period.
Acetone is a substance produced by the body as it tries to make up the glucose absent from low-carbohydrate diets.
Wayne Jones, a professor in experimental alcohol research at the University of Linkoping in Sweden, told the BBC breathalysers can sometimes fail to distinguish acetone from drink.
"Then there's a risk you get a false positive reading," he said.
Pilots, navigators, flight engineers and cabin crew are allowed to drink ahead of a flight, subject to a limit of nine microgrammes of alcohol in breath, compared with 35 microgrammes for motorists.
The aircraft was at the terminal gate when the pilot was arrested under the Railways and Transport Safety Act 2003.
The flight to JFK airport was delayed for an hour while the airline found another pilot to take charge.
"He has been cleared and is over the moon. He is now free to resume his flying career," a Virgin Atlantic spokesman said.
"It has been a tough week for him but he is now delighted."