POLICE have ruled out 96 people of interest but made no arrests in an “exhaustive” investigation into drones that caused chaos at Gatwick airport last Christmas.

At least two drones were the cause of Christmas chaos at Gatwick airport last year, the investigation found.

Police say the drones were in operation by a suspect, or suspects, who had “detailed knowledge” of the airport.

But police now say there are “no further realistic lines of enquiry” to pursue.

The incident is not believed to be terror-related or state-sponsored.

Gatwick was closed for 30 hours around the busy holiday period in December last year due to drone sightings.

More than 1,000 flights were disrupted, affecting about 140,000 passengers.

Now Sussex Police Assistant Chief Constable Dave Miller’s investigation has found at least two drones were behind the disruption.

“This was a serious and deliberate criminal act designed to endanger airport operations and the safety of the travelling public,” ACC Miller said.

“A drone strike can cause significant damage to an aircraft in flight and it is important to emphasise that public safety was always at the forefront of our response.

“No aircraft was damaged or passenger injured.”

Seven police forces have been involved in the investigation, which has cost £790,000.

Witnesses including a pilot and airport workers reported 129 separate sightings of drone activity.

Police believe drones appeared on 12 separate occasions across three days, varying in length between seven and 45 minutes.

On six occasions, witnesses spotted two drones flying simultaneously.

ACC Miller: “This is 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.

After an “exhaustive criminal investigation”, ACC Miller said there were “no further realistic lines of enquiry”.

He said: ““Measures now available have strengthened our capability to respond to and investigate a similar incident in the future.”

With support from national experts, we have carried out an exhaustive criminal investigation.

“But, without new information coming to light, there are no further realistic lines of enquiry at this time.”

The investigation involved 1,200 house-to-house enquiries.

Mutual aid and additional officer shifts ensured frontline policing in Sussex remained unaffected while the investigation occurred, a Sussex police spokeswoman said.

The force will continue to share learning from the incident across policing and other relevant agencies across the UK and the world.

The Gatwick incident is expected to be debated by officers and councillors at the Police and Crime Commissioner’s performance and accountability meeting next month.