Tens of thousands of passengers at one of Britain’s busiest airports have been left stranded after flights were canceled because of two drones that were spotted flying near the runways. Authorities believe the drones were a deliberate attempt to disrupt travel. Police said the drones were of an “industrial specification,” rather than a toy or amateur unmanned aircraft. Flights are unable to take off or land and, the BBC reports, around 110,000 passengers on 760 flights have been unable to take their scheduled journeys. Local police have appealed for information on Twitter to help them identify who is flying the drones, and said there’s “absolutely nothing to suggest that this is terrorism-related.”

Gatwick Chief Operating Officer Chris Woodroofe said police don’t want to shoot down the devices in case people are injured by stray bullets. The airport said there was still “ongoing drone activity” as of 9:30 a.m. local time and it’s unclear when the situation will be resolved. Woodroofe told the BBC two drones had been seen flying “over the perimeter fence and into where the runway operates from,” adding that police were searching for the operator so they could disable the drones. In England, it’s illegal to fly a drone within 1km (0.62 miles) of an airport or airfield boundary.