The repeated sightings of drones at the Sussex airport caused flights to be cancelled for nearly two days in December costing easyJet around £5 million from cancelled flights and lost revenue, plus another £10 million in “customer welfare” costs.

The airline was forced to cancel more than 400 flights due to the drone disruption, which affected 82,000 of easyJet’s customers.

Despite this disruption and impending Brexit on March 29, easyJet said it had seen “robust” customer demand during its first quarter up to December 31.

Johan Lundgren, easyJet’s chief executive, said: “EasyJet has made a good start to the 2019 financial year with robust customer demand and ancillary sales, driving solid revenue generation.

“This was underpinned by good operating and on-time performance across the network, with the exception of the disruption caused by the Gatwick closures due to drone sightings.

“There has been be a one-off cost impact from this incident, but underlying cost progress is in line with expectations. I am proud of the way our teams worked around the clock to mitigate the impact of the incident and looked after affected customers.”

EasyJet’s revenue rose by 13.7% to £1.3 billion for the quarter with passenger numbers rising by 15.1% to 21.6 million, although the airline’s capacity increase was “slightly lower than originally planned” due to the drone disruption and the late deliveries of new A321 aircraft from Airbus.

Lundgren added that bookings for the first six months of 2019 “remain encouraging” despite the continuing Brexit uncertainty.

“Second-half bookings continue to be ahead of last year and our expectations for the full year headline profit before tax are broadly in line with current market expectations,” said Lundgren.