Ten thousand passengers have suffered flight chaos after the runway at Gatwick Airport was closed due to drones being flown nearby.
Flights in and out of the UK's second busiest airport were suspended at about 9pm on Wednesday after two of the devices were seen near the West Sussex airfield.
Gatwick announced the runway had reopened at about 3am on Thursday, but 45 minutes later it was shut again after a further sighting of drones.
Chris Woodroofe, Gatwick's chief operating officer, said drones had been spotted over the airport as late as 7am on Thursday.
He blasted the "irresponsible" act, telling BBC Radio 4's Today programme that 10,000 people had been affected by the closure, including 2,000 whose flights had been unable to take off.
He said two drones had been seen flying "over the perimeter fence and into where the runway operates from".
Mr Woodroofe added that 20 police units from two forces were hunting for the pilot, saying: "The police are looking for the operator and that is the way to disable the drone.
"We also have the helicopter up in the air but the police advice is that it would be dangerous to seek to shoot the drone down because of what may happen to the stray bullets."
Passengers faced severe disruption as some flights were unable to leave the tarmac while others were diverted to other 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 hotel accommodation or transport for those whose flights were diverted.
Aviation website airlive.net said inbound flights were diverted to a range of UK airports as well as Amsterdam and Paris.
Lyndsey Clarke, from Southend, said she was stuck on a plane for more than four hours after it was rerouted to Stansted.
The 27-year-old said passengers were 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."
Joe Bond's flight from Belfast was diverted to Birmingham, and he joked on Twitter: "From the sound of the stewards we might be staying here forever."
He added: "Update. Got a free can of Coke and Pringles. Which has made the delay better."