Drone sightings kept London Gatwick Airport closed for a second day, derailing trips of tens of thousands of travelers ahead of Christmas, while the military was called up to assist with what local law enforcement called a "deliberate act."
Flights were suspended as law enforcement searched for the operator of what it called an "industrial drone."
The drones appeared to be "a deliberate attempt to disrupt flights," said a statement from the airport, the second-busiest in the U.K. after London Heathrow. Hundreds of flights were grounded, while scores of others were diverted to other airports. London Gatwick, which serves more than 100,000 passengers a day, said disruptions would continue on Friday.
The drone flights near Gatwick's airfield did not appear to be an act of terror, according to Sussex Police. British armed forces were called in to help local law enforcement with "specialist equipment," Britain's Ministry of Defense said Thursday.
Two drones were sighted near Gatwick's airfield on Wednesday night around 9 p.m. GMT, but the airport is "still receiving drone sightings" in the area, the airport's CEO Stewart Wingate said in a statement.
"Therefore, until we are confident that the issue has been resolved it would clearly not be in the interests of passengers to do so as we could be jeopardizing their safety," he said.
The incident highlights concerns among air safety regulators about preventing drones from flying close to aircraft and airfields, as the devices become more popular and easily obtainable.
"It's something that's not been experienced in this country before," British Transport Secretary Chris Grayling told Sky News. "We've known for a while that drones were a problem around the world."
Government authorities in the U.S. and elsewhere have sounded alarms about the dangers if drones potentially collide with airliners. Researchers at the University of Dayton this summer released video of a test of how a drone could damage an aircraft. They released video of a 2.1-pound DJI Phantom 2 quadcopter tearing into the wing of a small propeller plane.
"The incident today where unauthorized drone activity impacted flight operations at Gatwick airport clearly demonstrates that [unmanned aircraft system] operators' intent to cause disruption or harm which can create significant risks to the safety and security of the populace," said U.S. Department of Homeland Security spokesperson McLaurine Klingler.
Restrictions on nighttime flying were lifted at some U.K. airports in the area to accommodate passengers.
Airlines warned travelers not to come to the airport while operations were suspended and said there was no indication of when the airport would reopen.
Low-cost airline Ryanair said its flights scheduled to fly from Gatwick on Friday would instead operate out of London Stansted Airport, about 70 miles away.
Airlines said passengers affected by the closure can change their flights for free and receive compensation. Budget carrier easyJet cancelled all of its flights scheduled for Thursday and said it would reimburse the "reasonable expenses" of travelers who arrange for alternative transportation.