The chief executive of Gatwick Airport says the major disruption at the airport after drone sightings is the result of "highly targeted activity... designed to close the airport and bring maximum disruption in the run up to Christmas".
Earlier, the London airport - which is the second busiest in the UK - says the suspension of flights was due to, what appears to be, "a deliberate attempt" at disruption.
There have been no flights in or out of the airport since this morning, after drones were seen flying close to the runway.
The airfield shut for several hours on Wednesday night, re-opened for a short while and then closed again when another drone was reported.
Further drone sightings have since been reported, with authorities saying flights will not resume until they're confident the issue has been resolved.
Tens of thousands of passengers have been affected by the situation, and almost every flight due out of the airport tonight has been cancelled.
The disruption is set to run into tomorrow, with the airport now urging anyone due to fly tomorrow to check with their airline before leaving.
Irish flights are among those affected.
Aer Lingus says disruptions and cancellations are expected, and that passengers should check your flight status before departing for the airport.
Flight disruptions and cancellations are expected due to the closure of airspace over Gatwick. Please check your flight status before departing for the airport. Affected guests can be accommodated on the next available flight or cancel and apply for a refund.
— Aer Lingus (@AerLingus) December 20, 2018
In a statement this evening, Gatwick CEO Stewart Wingate apologised to passengers.
He said: “On behalf of everyone at Gatwick I would like to repeat how sorry we are for the inconvenience this criminal behaviour has caused passengers and we share their real anger and frustration that it has happened.
"This is a highly targeted activity which has been designed to close the airport and bring maximum disruption in the run up to Christmas. We are working very closely with the police and the security services to try to resolve this for passengers."
He added that authorities at the airport still aren't in a position to say when it will be safe to reopen.
"Deliberate attempt"
In a statement earlier, Gatwick Airport said they are investigating alongside Sussex Police.
It says: "All flights remain suspended from Gatwick today, due to ongoing drone activity around the airfield.
"There is significant disruption, as a result of what appears to be a deliberate attempt to disrupt flights.
"We are extremely disappointed that passengers are being affected, especially at this time of year.
"Our advice continues to be not to travel to the airport and to check with your airline on the status of your flight."
1/2 Thursday 11.45: All flights remain suspended from Gatwick today, due to ongoing drone activity around the airfield. There is significant disruption, as a result of what appears to be a deliberate attempt to disrupt flights.
— Gatwick Airport LGW (@Gatwick_Airport) December 20, 2018
The Gatwick Express train service has offered to bring passengers with a valid Gatwick ticket to Luton Airport at no extra cost.
It is also waiving fees for those who cannot travel or need a refund.
📢 Have you been affected by the #drones at Gatwick ✈ï¸? If your travel plans have been changed, we’ve made the following arrangements to help get you on the move without any further hassle.
â„¹ï¸ Info here 👉 https://t.co/YLA9Cox16Y pic.twitter.com/ICS7fYmGeK
— Gatwick Express (@GatwickExpress) December 20, 2018