A drone "put 130 lives at risk" after it nearly hit an aircraft approaching London Gatwick, a pilot said.
The flying gadget passed directly over the right wing of the Airbus A319 which was preparing to land at the West Sussex airport, according to the UK Airprox Board (UKAB).
It was described as "very large, certainly not a toy", with four blades and a diameter of about one metre.
The plane's first officer told investigators that the "startle factor of the drone's proximity" nearly caused him to disconnect the cockpit's autopilot system and take "avoiding action".
A safe landing was completed despite the presence of thedrone but the UKAB warned: "A larger aircraft might not have missed it, and in the captain's opinion it had put 130 lives at risk."
The incident on July 9 was classed as having the highest degree of risk as "providence had played a major part" in a collision being avoided.
The airline involved and the origin of the plane was not identified by the UKAB.
Former RAF and British Airways pilot Steve Landells described the incident as "another worrying near-miss that could have ended in tragedy".
It was one of 18 near-misses involving drones, balloons or other objects investigated at the latest UKAB meeting.
In July the Department for Transport unveiled plans to launch a drone registration system after research found the devices could smash plane windscreens.
Mr Landells, flight safety specialist at pilots' association Balpa, told the Press Association: "We can't allow the programme of action to slip. Balpa is keen to see details of what this potential new legislation will look like and set a timescale for its implementation.