Police are appealing for information as they hunt for a drone which grounded flights at Heathrow yesterday.
Officers were sent to the scene as a suspected drone was spotted flying over the countrys busiest airport at around 5pm yesterday afternoon.
Flights were grounded as police investigated the sightings, and the army has been brought in to help.
Now Scotland Yard is appealing to the public for information which could lead to the pilot.
Commander Stuart Cundy said: “Our priority is keeping the airspace over London's airports safe for the thousands of planes flying in and out every week.
“Any deliberate acts to endanger the airfield and aircraft are serious offences that can carry lengthy prison sentences. If flown into the path of an aircraft, a drone has the potential to cause great harm to those on-board. Anyone caught illegally operating drones will be dealt with robustly.
“We understand the extensive frustration and inconvenience that suspending flights causes the public.”
Flights resumed at around 6pm after air traffic control gave the thumbs up.
This is the second time in under a month that a drone has wreaked havoc at a major UK travel hub.
Dozens of flights were cancelled in December when a suspected drone repeatedly flew over Gatwick, affecting hundreds of thousands of Christmas travellers.
The government has promised to give police new powers to seize drones and will extend exclusion zones around airports from one to five kilometres.
Defence secretary Gavin Williamson said: “Last night, at the request of the Metropolitan Police, our armed forces deployed to assist and support them.
“Our armed forces are always there when needed, ready to support the civilian authorities with our capabilities.”