Two drones found by police near Gatwick Airport have been ruled out of involvement in the incident which disrupted hundreds of flights before Christmas, Sussex chief constable Giles York has said.
Mr York told BBC Radio 4's Today programme that police have searched 26 potential launch sites for drones near the airport but do not believe they have found the drone believed to have been flown near runways on December 19 and 20.
"I don't think we have found the drone responsible for this at this time," said the Chief Constable.
"I think the fact that we have found two drones so far as a result of this does show the extent of the search that has been carried out. I am led to believe that we are able to rules those drones out of this investigation at this time."
Mr York said he was "absolutely certain that there was a drone flying throughout the period that the airport was closed".
Police received 115 reports of sightings in the area, including 92 which have been confirmed as coming from "credible people", he said.
Mr York said he was "really sorry" for Paul Gait and Elaine Kirk, who said they felt "violated" after being questioned for 36 hours in custody before being ruled out of involvement in the disruption of Gatwick.
However, he said he was "convinced that the grounds for arrest - the lawful suspicion - in the first instance was well-founded".
The Chief Constable said: "I'm really sorry for what he has experienced and the feeling of violation around it.
"I am really sorry for what he went through, but the reason why we held him was so that we could dispel everything in the first instance. What might have been worse as an experience for him would have been to be released under investigation still.
"That's why we took the time - in order to allow him the best opportunity to put his life back on the rails."
Mr York confirmed that military technology was now in place at Gatwick, though he declined to identify the nature of the equipment.
"The systems that are in place today are dramatically different to what was in place a week ago," he told Today.
Asked whether he could rule out a repeat of last week's disruption, Mr York said: "I don't think you can ever rule out anything happening again.
"But what we can say is what is at the heart of this is ensuring it is safe for the aircraft to take off and that's the different position that Gatwick Airport finds itself in today."
- Press Association