Britain’s second-busiest airport has suspended all flights “due to an air traffic control systems issue”.
The airport said: “We are working with ANS, our air traffic control provider, to rectify this issue as quickly as possible.
“We apologise and advise passengers to check with their airline or on our live flights page for the latest flight information.”
The problem relates to the control tower.
Gatwick has the busiest runway in the world, with a take-off or landing every 80 seconds at peak times.
Arriving aircraft are already being diverted.
Even if a swift fix is found to the problem, disruption will continue well into the evening.
Shortly before Christmas, Gatwick airport was closed for 33 hours, disrupting the plans of 160,000 passengers, because of unauthorised drone activity.