A drone came so close to a London-bound passenger jet that the crew believed it must have collided with the tail.
The aircraft, an Airbus 321, was flying over Kew in west London on approach to Heathrow when the incident happened.
A report by the UK Airprox Board (UKAB) said a three or four-engine white drone came to within just five feet over the first officer’s window.
It stated: “The crew considered that the drone passed close enough that it must have collided with the tail.”
The aircraft was inspected by engineers after landing but they found “no tangible evidence of collision”.
The incident happened on 25 October 2017 as the jet flew at an altitude of 1,700 feet and the UKAB put it in the highest category of risk.
“Providence had played a major part in the incident and/or a definite risk of collision had existed,” the report concluded.
The UKAB did not disclose the identity of the aircraft involved.
A draft drone bill is due to be published by the government later this year which will require drone users to register and complete safety awareness tests.
Flying drones near airports or above 400 feet could also be included in the new regulations.
Last July a drone almost hit a plane coming in to land at London Gatwick putting 130 lives at risk.