The chaos caused by drones at Gatwick Airport in December 2018 was carried out by operators with a "significant knowledge" of airport operations, according to the Chief Constable of Sussex Police.
The claim was made by Giles York on Friday morning in a webcast, as he was questioned by Police and Crime Commissioner Katy Bourne.
The Chief Constable described this as an "unprecedented illegal drone incursion" and a "deliberate criminal act".
The disruption meant 1,000 flights were disrupted affecting 140,000 passengers.
Two drones were spotted on and off over a period of 30 hours.
The police chief has admitted the anti-drone system in place at the time just could not cope.
Giles York, Chief Constable of Sussex Police
Eight hundred officers from seven different forces were involved in the investigation which has cost almost £800,000.
No-one has ever been charged and there are no active lines of inquiry.
Katy Bourne, Sussex Police and Crime Commissioner
Ten months on, it is still unknown who was flying those drones and nobody has ever claimed responsibility.
It comes as the retailer John Lewis has decided to stop selling drones as it is worried about them being misused.