Dec. 21 (UPI) -- Flights to and from London's Gatwick Airport were briefly suspended again on Friday after a new drone sighting at the airport was reported.
The airport, Britain's second-largest, closed for 36 hours, starting on Wednesday, after drones were discovered. Limited service resumed on Friday morning, after two drones were discovered, about hours apart. The incidents closed the airport, which was then reopened and closed again for about an hour Friday afternoon over an unconfirmed report of a drone.
Flights were grounded and inbound planes diverted starting at 9 p.m. Wednesday and holiday travel for thousands of passengers on 160 canceled flights was disrupted. Another 682 flights were at risk of being delayed or canceled Friday.
More than 50 drones were detected in the 24 hours since the first appearance, Detective Chief Superintendent Jason Tingley of Sussex Police said. He said they were following up a "number of persons of interest" in their investigations.
Prior to Friday's shutdown of the airport, many departing flights took off after delays. While police did not specify their methods of investigation, photos from Gatwick suggest military-grade signal jamming and drone-tracking equipment is in use, The Guardian reported on Friday.
Police said they do not link the drone sightings to terrorism, but it is possible the drones are an environmental protest.
"In terms of motivation there is a whole spectrum of possibilities, from the really high-end criminal behavior all the way down to just individuals trying to be malicious," said Steve Barry, Sussex assistant chief police constable.