London’s Gatwick airport is closed to aircraft following multiple sightings of illegal drones, disrupting flights for as many as 115,000 people on one of the busiest travel days of the year.

Reports of two objects above the airfield prompted authorities to halt services at about 9 p.m. Wednesday, with more than 50 incoming planes diverted to terminals across Britain and some in mainland Europe. The airport reopened after six hours, only to shut again 45 minutes following further sightings.

Operations remained suspended into the peak morning departure period, with no time set for their resumption, though a spokeswoman said daylight should help staff determine whether there is still a risk. Gatwick is the world’s busiest single-runway hub, the biggest base for discount carrier EasyJet Plc and the focus for long-haul leisure flights at British Airways.

Gatwick said on its Twitter feed that services had been idled due to “drone activity” and that customers should check with their airline before heading to the airport. “We’re sorry for the inconvenience today, but the safety of our passengers and staff is our no. 1 priority,” it added.

Diverted or canceled flights overnight affected about 6,000 people at carriers including Cathay Pacific Airways Ltd. and Norwegian Air Shuttle ASA, while 2,000 more were unable to depart on 18 scrapped services. The extended closure means hundreds of daytime operations may be lost in what would be one of the worst-ever disruptions to schedules by drone illegal incursions.

Even when the airport reopens, further upheaval is likely, with EasyJet saying in a statement that the overnight shutdown has left aircraft and crew rostered to fly from Gatwick stranded at other locations.

London is served by about half a dozen airports, and some passengers at Gatwick said they were seeking to book flights from Heathrow, about 30 miles away, in order to complete their journeys.

Others tweeted their frustrations while generally supporting the airport’s decision to close. “Right call Gatwick,” one person said, though another suggested that police should seek to shoot down any trespassing craft, and a third argued that with day dawning “either you can see a drone or you can’t.”

Unmanned aerial vehicles and laser pointers are becoming an increasing threat for aircraft, prompting regulators to come up with new rules against operating the devices near airfields.

Earlier this year, airspace around Wellington, New Zealand, was closed for 30 minutes after a drone was spotted flying extremely close to the runway. In 2016, Dubai International Airport was closed temporarily.

Different Birds

“In the past, trying to skirt around birds was hard enough and now you’ve got a different kind of bird made out of metal or plastic,” said Mohshin Aziz, an aviation analyst at Maybank Investment Bank Bhd. in Kuala Lumpur. “A drone strike is far, far more damaging than a bird strike.”

Last week, Grupo Aeromexico SAB said it’s investigating whether a drone slammed into a Boeing Co. 737 aircraft as the plane approached Tijuana, Mexico. The jet sustained damage to its nose but landed safely.

While most nations prohibit drones flying in paths reserved for airliners, the millions of small consumer devices that have been purchased around the world can’t be tracked on radar. That makes it difficult to enforce the rules. In addition, many users don’t know the restrictions — or don’t follow them.

–With assistance from Rita Devlin Marier and Ellen Milligan.

©2018 Bloomberg L.P.

This article was written by Justin Bachman, Kyunghee Park and Christopher Jasper from Bloomberg and was legally licensed through the NewsCred publisher network. Please direct all licensing questions to legal@newscred.com.

Photo Credit: An Easyjet plc aircraft, left, taxis along the tarmac at London Gatwick Airport in London, U.K., on Wednesday, Oct. 14, 2015. Chris Ratcliffe / Bloomberg