An airline pilot has reported a near-miss with a "rugby ball-shaped" UFO that passed within a few metres of his passenger jet near Heathrow airport.
He told British aviation authorities investigating the incident last July that he was certain the object was going to crash into his aircraft and that he ducked as it headed towards him.
They have been unable to establish the identity of the mysterious craft, which apparently approached the airliner at great speed.
The daylight incident occurred while the Airbus A320 of an unnamed airline was cruising at 34,000 feet, around 32km west of the airport.
The investigators' report states: "He was under the apprehension that they were on collision course with no time to react. His immediate reaction was to duck to the right and reach over to alert the FO [first officer]; there was no time to talk to alert him."
It adds: "The captain was fully expecting to experience some kind of impact with a conflicting aircraft."
He told investigators the object passed "within a few feet" of the top of the jet and that it was "cigar/rugby ball-like" in shape, bright silver and "metallic" in construction. The episode was examined by the UK Airprox Board, which studies "near misses" involving aircraft in British airspace.
It checked data recordings to establish what aircraft were in the area but eliminated them all, along with meteorological balloons.
Military radar operators were also unable to trace the reported object.