Gatwick’s runway has reopened after drones caused the airport to shut down for more than a day.
The airport, the UK’s second busiest, said 765 flights were scheduled for departure and arrival.
Boss Chris Woodroofe said police had not yet found the drone operator.
Police said it was possible they were an environmental activist.
He said extra “mitigating measures” from the government and military had given him “confidence to reopen”.
Thousands of passengers remain stranded at Gatwick as police continue their search for those responsible for the chaos, which started on Wednesday night.
The airport could not operate while the drones were in flight in case they hit and damaged a plane.
Officers have so far failed to locate the “industrial specification” drones or their pilot and had been considering plans to shoot a device down.
But Steve Barry, assistant chief constable at Sussex Police, said they were in a “much better position today”.
He told BBC Breakfast there were a “number of lines of inquiry” into the “very malicious and criminal behaviour”, including the possibility it could have been the work of an environmental activist.
Mr Barry said a drone had last been seen at 22:00 GMT on Thursday.
Transport Secretary Chris Grayling said there was no evidence it was terror-related.
But he called it a type of disruption “we’ve not seen before” and “lessons need to be learned”.
He said the situation was “unprecedented, anywhere in the world”.
