The drone attack that disrupted Gatwick for three days in December cost the airport £1.4m.

While early estimates of the costs ran into tens of millions, the brunt has been borne by airlines – although Gatwick has since spent an extra £4m on anti-drone technology.

The airport was closed for 36 hours and then shut down again briefly on 21 December after multiple reported sightings of a drone or drones in the vicinity.

Police and military were called in to help at Britain’s second-largest airport, but the perpetrator was never found. More than 1,000 flights were disrupted in the runup to Christmas, with 140,000 passengers affected.

EasyJet, which operates about half of all flights at Gatwick, said the attack cost it £15m in compensation and welfare payments to passengers, as well as lost revenue.

Announcing annual profits of £208m, the chief executive of Gatwick, Stewart Wingate, said he “fully stood by the decisions taken back then” to close the airport. He added: “When we came under a sustained attack, as we did, we didn’t waver.”

He claimed Gatwick had installed “some of the most sophisticated counter-drone equipment of any airport in western Europe”.

Wingate admitted the attack may have been an inside job. He said: “There are many other potential sources and it’s an ongoing investigation.”