Police will remain on high alert at Gatwick Airport as staff work through a backlog of cancelled and delayed flights following days of drone-related disruption.
Flights were briefly grounded at the airport on Friday evening after a fresh sighting at around 5.10pm, but military measures reassured operators it was safe to reopen the runway shortly afterwards.
Despite flights resuming after 70 minutes, airlines were still cancelling and delaying outbound flights throughout the evening and into the night.
Inbound flights were also operating with delays, with some scheduled to arrive at Gatwick in the early hours of Saturday.
Police believe more than one unmanned aircraft are responsible for the drone activity and are investigating the possibility of multiple culprits.
Sussex Police had said the suspension on Friday was provoked by “reports of renewed drone activity” while the force was “deploying significant resources to seek and locate the drone and its operator”.
Police prepared to blast the drones out of the sky with a shotgun or jam them with a hi-tech radar system as they continued their hunt for the aircraft and their operators.
Inside the airport, passengers expressed their anger at the ongoing disruption.
A passenger due to fly to Sicily on Thursday said she was considering renting a car and driving there after her second flight in two days was cancelled following the fresh sighting.
Laura Cammarata, 27, who lives in London, was due to travel to the island with her partner for Christmas. She told the Press Association she was frustrated after their flight rescheduled from Thursday to Friday was cancelled.
Ms Cammarata said: “We did the whole process again, we got the train, we started queuing up and at some point they said it’s cancelled again.
“We’re trying to re-book and they’re saying they can’t book us on.”
Her partner Giuseppe Alia, 28, also from London, said: “They should have some contingency to get people to other airports, I understand it’s not their fault but they should force airlines to collaborate in this situation.”
Military equipment was being used to stop further drone disruption while a range of tactics are in place if any unmanned aircraft are seen inside the perimeter.
One piece of equipment believed to have been deployed at the airport is the Israeli-developed Drone Dome system, which can detect drones using radar.
It can also jam communications between the drone and its operator, enabling authorities to take control of and land the drone.
Sussex Police Assistant Chief Constable Steve Barry said less sophisticated options are also available, including shotguns, although blasting drones out of the sky was one of the least effective tactics.
Police are keeping an open mind over the motive, with theories including an environmental protest, but they are not treating it as a terrorist incident.
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Mr Barry said there is no evidence of involvement of a foreign power, but described the drone activity as “really high-end criminal behaviour”.
“This is a really significant criminal offence,” he said.
“There are resources here at Gatwick Airport now to mitigate the threat of that and a lot of resources to bring the offender to justice.”
The Government denied accusations that it had been slow to combat the threat from drones, and had delayed plans to introduce laws to regulate their use.
Shadow transport spokesman Andy McDonald has said the Government had been too slow to act, despite growing concern over increasing numbers of near misses between drones and manned airports.
The Times reported that Transport Secretary Chris Grayling had shelved plans to introduce legislation amid pressure on his department, with civil servants being diverted to prepare for Brexit.
But a Department for Transport spokesman said: “These claims are a combination of nonsense and gross misrepresentation.
“The drones at Gatwick have been flown illegally. The Government changed the law this year to make it illegal to fly drones within 1,000 meters of an airport or above 400 feet.
“The law couldn’t be any more clear: those found endangering aircraft face significant jail terms. Next year further laws will come into effect to ensure drone users must be registered and pass safety tests.
“We are continuing to introduce further measures and recently consulted on extending police powers to deal with people who misuse drones, as well working on the development of counter-drone technology to ensure incidents like this can’t happen again and to ensure aviation is well protected from incidents like this in the future.”
Crimestoppers offered a £10,000 reward for information that leads to the culprit being caught. The charity can be contacted anonymously on 0800 555 111.