Sussex Police's chief constable has said he feels "really sorry" for the couple who were held for 36 hours over the Gatwick Airport drones chaos.
Paul Gait and Elaine Kirk, who were released without charge, said they felt "violated" after their home was searched and their identities exposed.
Giles York told the BBC Radio 4's Today programme he was "convinced the grounds for arrest were well-founded".
Two drones found near the airport have been ruled out of being involved.
Mr York defended the decision to hold Mr Gait for an extended period, despite his employer saying he was at work during the drone flights.
He added: "I'm really sorry for what [Mr Gait] has experienced and the feeling of violation around it.
"[But] what might have been worse as an experience for him would have been to be released under investigation still.
"We were able to exhaust all our lines of inquiry on that first instance and were able to release him from police custody saying he was no longer a suspect."
About 1,000 flights were affected during the chaos between 19 and 21 December when drones were seen near the runway.
A suggestion by a senior Sussex police officer that there may have been no drones was later dismissed as a "miscommunication".
Mr York said police received 115 reports of sightings, including 93 confirmed as coming from "credible people", which he later said included a pilot, airport staff and police officers.
He admitted police drones launched to investigate could have caused "some level of confusion".
However, the Sussex force later denied the use of police drones had caused any disruption.
See our renewed appeal in the investigation of illegal drone use at #Gatwick ⬇️— Sussex Police (@sussex_police) December 29, 2018
The disruption was not caused by police drones, launched in response and only when the airport was closed. https://t.co/fzfvGe13ZY
Mr York revealed two drones found by police near the airport had now been ruled out of causing the chaos, which saw flights cancelled or diverted.
Despite searches of 26 potential sites, he said: "I don't think we have found the drone responsible."
However, he said he was "absolutely certain that there was a drone flying throughout the period that the airport was closed".
He confirmed military technology had been installed following the incidents, "dramatically" improving security at the airport, but said he could not rule out future disruption of the same kind.
Sussex Police has renewed its appeal for help to find "the criminal whose activities led to widespread disruption".
Mr York said: "Public safety remains a priority and what we are dealing with is both unprecedented and challenging.
"There will be information relevant to this inquiry within the community and, with a £50,000 reward on offer for information from Gatwick Airport Limited, it is vital that people come forward so we can bring to justice the person responsible for this criminal act."