According to a study into the dangers of unmanned aircraft, the threat of a drone being flown into a commercial jet was the "biggest risk", said Colin Smith, Detective Chief Inspector, a counter-terrorism adviser at the Home Office.
Security and defence officials also fear that drones could be used by groups such as ISIS to score a propaganda coup.
Passenger jets are being put at risk on a weekly basis by drones being flown close to them, Smith said, adding that drones could also be used to launch terrorist attacks.
Smith recalled how a drone pulling a pro-Albanian banner had been flown into a football stadium in Belgrade during a Euro 2016 qualifier last year, setting off crowd violence and forcing the match to be abandoned.
"As an embarrassment factor, change that to an ISIS flag and fly that down Whitehall during Remembrance Sunday.
Who's going to be able to stop that flag being flown? It is a real and current problem," he was quoted as saying by the 'The Sunday Times'.
There have been a series of potentially fatal near misses close to British airports in the past year, with drones being spotted near airliners at heights of up to 5,000ft, the report said.