Passenger were affected overnight on Wednesday as flight were unable to take off or land.
Flights of Tens of thousands of passengers were disrupted by drones flying over one of the UK’s busiest airports;
two devices were seen flying over the perimeter fence.
The airport official said a drone had been spotted “in the last hour” and the runway would not open “until it was safe to do so”.
About 110,000 passengers on 760 flights were due to fly on Thursday. Disruption could last “several days”.
Those due to travel have been told to check the status, while EasyJet told its passengers not to go to Gatwick as their flights have been cancelled.
Sussex Police said it was not terror-related but a “deliberate act” of disruption.
Dr Alan McKenna, from the University of Kent, said the drones appeared to be “of an industrial size” not “one you can buy from the shops”.
The runway briefly reopened at 03:01 but was closed again about 45 minutes later amid “a further sighting of drones”.