The runway at Gatwick remains closed on Thursday morning following reports of drones flying close to the airport - despite briefly reopening overnight.
Flights in and out of the airport were suspended at about 9pm on Wednesday after two drones were sighted near the airfield.
Gatwick announced that the runway had reopened at about 3am on Thursday - but just 45 minutes later it was shut again.
In a statement, the airport said: "Following reports of two drones flying over the Gatwick Airport airfield at around 9pm, the airfield was closed from 21.03 on Wednesday 19th December to 03.01 on Thursday 20th December.
"Unfortunately a further sighting of drones in the vicinity of the airport has forced the runway to be closed again from 03.45 as we investigate the sighting alongside Sussex Police.
"We will update when we have suitable reassurance that it is appropriate to reopen the runway."
'It was just chaos'
Passengers faced delays to their travels on Wednesday night as some flights were unable to leave the tarmac while others were diverted to alternative airports.
Some people reported being left stuck on planes for several hours while they waited to find out what was going on.
Gatwick advised anyone flying from the airport, or collecting someone, to check the status of their flight.
A spokeswoman added that airlines were working to provide affected passengers with hotel accommodation or transport for those whose flights were diverted.
Lyndsey Clarke, from Southend on Sea, said she was stuck on a plane for more than four hours after it was re-routed to Stansted.
The 27-year-old said passengers were then having to get taxis back to Gatwick after they were finally allowed off the aircraft.
Luke McComiskie's plane ended up in Manchester, and he described chaotic scenes as people tried to find their way home after more than three hours stuck onboard.
The 20-year-old from Aldershot told the Press Association: "We got told there would be some arrangements with coaches for us when we get out the terminal... it was just chaos and they had only two coaches and taxis charging people £600 to get to Gatwick."