Police investigating a drone attack at Gatwick Airport say they are no closer to finding the people responsible.
Flights were suspended for 30 hours after the drone sightings in December, causing chaos for 140,000 passengers.
Sussex Police said they received 129 separate reports of drone activity at the time, with 109 from "credible witnesses" including a pilot and airport police.
The force say they have ruled out 96 people of interest.
Without new information coming to light, there are "no further realistic lines of inquiry at this time", police added.
In July a senior officer said they believed two drones were simultaneously used in the attack.
The incident was not deemed terror-related and there is no evidence to suggest it was either state-sponsored, campaign or interest-group led. No further arrests have been made.
The criminal investigation by Sussex Police, with support from national expertise, has identified, researched and ruled out 96 people "of interest".
The policing operation and subsequent investigation has cost £790,000 and is not expected to increase further, with the bulk of the cost relating to the operational police response.
Through corroborated witness statements, it is believed the offender, or multiple offenders, had detailed knowledge of the airport.
Witness statements show activity happened in "groupings" across the three days on 12 separate occasions, varying in length from between seven and 45 minutes.
On six of these occasions, witnesses clearly saw two drones operating simultaneously.
Sussex Police's Assistant Chief Constable Dave Miller said: "This was an unprecedented set of circumstances for all agencies involved at a time when the police and the Government were at the early stages of assessing domestic counter drone technology.
"Equipment was quickly installed using both military and private assets to bring it to a conclusion and allow the airport to reopen. Measures now available have strengthened our capability to respond to and investigate a similar incident in the future."