The Gatwick Airport, which serves United Kingdom’s London, reopened on Friday after shutting down operations for more than a day due to repeated drone sightings, BBC reported.

“Gatwick’s runway is currently available and a limited number of aircraft are scheduled for departure and arrival,” the airport’s official Twitter handle said.

The runway at the Gatwick airport had been closed since 9 pm Wednesday (2.30 am on Thursday Indian time), except briefly opening for 45 minutes on Thursday, after two drones were spotted near the airfield. Police said there had been more than 50 sightings of the drones in 24 hours from when the runway was first closed, according to The Guardian.

The airport management said at least 140 flights were cancelled and nearly 1.26 lakh people were stranded at the airport between Wednesday and Thursday. Around 700 flights were scheduled to depart from the airport on Friday ahead of Christmas.

Gatwick’s Chief Operating Officer Chris Woodroofe said the police had not yet located the drone operator, but the airport has put in additional mitigating measures with the help of government agencies and the military to protect against drones.

Transport Secretary Chris Grayling said the government was doing “everything to make arrangements with other airports”. Grayling said night-flight restrictions at other airports had been lifted so that “more planes can get into and out of the country”.

Police Superintendent Justin Burtenshaw, head of armed policing for Sussex and Surrey, said finding the drone’s operator was “a difficult and challenging” prospect, according to BBC. “Each time we believe we get close to the operator, the drone disappears; when we look to reopen the airfield, the drone reappears,” he said.