A police investigation was launched after the pilot of a BA flight from Geneva on 17 April reported an object had struck the front of the aircraft.
It was thought to be the first drone collision with an aircraft in the UK.
The Airbus A320 was carrying 132 passengers and five crew as it approached the airport. It landed safely.
At the time the Metropolitan Police said the plane was hit by a drone at about 1,700ft (580m) while flying over the area of Richmond Park, in south west London.
The head of the International Air Transport Association, Tony Tyler, earlier this year warned that drones flown by the general public were "a real and growing threat" to civilian aircraft.
The UK Air Proximity Board - which investigates near-miss incidents in UK airspace - says there had been a number of serious near-misses at UK airports involving drones.
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