There were 18 near misses between aircraft and drones across Britain between July and October 2018, according to an air safety body.
Out of the reported incidents, 12 took place in Greater London.
The UK Airprox Board (UKAB) said the "highest risk of collision" occurred when a large "commercial drone" was seen to pass within 20 metres of an Airbus A380 as it approached Heathrow.
Drone sightings disrupted about 1,000 flights at Gatwick Airport in December.
Departures at Heathrow Airport were also halted temporarily after drone activity was reported earlier this month.
Heathrow has since deployed an anti-UAV defence system, which can detect, track and ground problem drones.
Aviation minister Baroness Sugg said: "The actions of these drone users were not only irresponsible, but illegal.
"The law could not be clearer that this is a criminal offence and anyone endangering others in this way faces imprisonment."
Outside of London, other incidents reported by the UKAB - which monitors near misses involving aircraft - occurred in Manchester, Cambridgeshire, Birmingham, Cardiff, Glasgow and the East Midlands.
The UKAB reported that one of the category A incidents took place as an Embraer 190 aircraft was landing at Glasgow Airport.
It concluded a "definite risk of collision" had existed, after a "shiny white drone" was flown directly above an airliner, just 15-30 metres away.
A total of 120 near misses between drones and aircraft were reported in the year between 4 December 2017 and 4 December 2018.