A US-bound British airliner had to be diverted to Canada after wrongly transmitting a hijack warning.
The Virgin plane was not allowed into US airspace
The Virgin Atlantic Airbus, carrying 273 passengers, was heading from London to New York when US aviation officials asked it to divert.
Two Canadian fighter jets escorted the plane to Halifax, in Nova Scotia.
Virgin said the plane's transponder, which sends data to radar stations and air traffic control, had inadvertently sent code used for hijack warnings.
The airline confirmed it had spoken directly to the crew and they were safe.
It said the false alarm was caused by a malfunction which meant that when the transponder began transmitting the 4-digit hijack code, the crew were unable to shut it off.
A spokesman later said: "Virgin Atlantic is investigating the technical reason for this.
"Passengers have been kept fully informed."
No-one on the flight, which left London Heathrow at 0859 BST on Friday for New York's JFK airport, was in any danger, she added.
North American Aerospace Defense Command Lt Cmdr Sean Kelly said Canadian fighter jets escorted the plane to Halifax, where it landed safely at 1539 BST.
Canadian military officials confirmed that two CF-18s from Bagotville, Quebec, were sent to intercept the flight.