A drone at 10,000ft narrowly missed an aircraft while on its approach to Heathrow, according to an official report.
Pilots spotted the drone with multiple arms and up to eight rotors pass just below the right wing of the Airbus A320 as it was preparing to land.
Both pilots exclaimed: “Was that a drone? At 10,000 feet!”, air safety experts UK Airprox Board (UKAB) said.
There was no time to react to the drone or to take avoiding action.
The drone was estimated to be about 98ft away from the aircraft and “safety was not assured”, UKAB added.
Large drones are not permitted to fly above 400ft or within proximity of airports or airfields.
The incident occurred on November 11 last year, so quickly the pilots said they had “no time to react”, the BBC reported.
The risk posed was classified as ‘B’, the second most serious out of five in which the safety of the aircraft may have been compromised.
Police officers were alerted at the time but they did not find the operator.
It was one of four near misses between aircraft and drones in the latest UKAB monthly report, bringing the total in the past 12 months to 59.
The government is considering mandatory registration for new drones to help regulate their use and the Department for Transport is consulting on how to improve drone safety.