LONDON (Reuters) – Flights from London’s Heathrow airport were halted for about an hour on Tuesday after reports of a drone sighting near Europe’s busiest air hub, raising fears that the chaos that affected rival Gatwick last month could be repeated on an even larger scale.

“We are responding to a drone sighting at Heathrow,” the airport said. “As a precautionary measure, we have stopped departures while we investigate. We apologise to passengers for any inconvenience this may cause.”

Commander Stuart Cundy, said: 
“Shortly after 17:00hrs today (8 January) we received reports of a sighting of a drone at Heathrow airport. As part of our established response plans to such an incident, officers were swiftly deployed across the airport and we continue to work closely with colleagues from Heathrow Airport Limited.

“As a precaution, departures were stopped at the airport whilst initial enquiries were made. Once it was established it was safe to do so, departures were resumed just after 18:00hrs and the airport is now fully operational.

“Our priority is to ensure that there is no ongoing threat to the safety of those at the airport and identify those responsible for this dangerous act.

“Police officers were amongst those who saw the drone and a full criminal investigation has been launched. We are carrying out extensive searches around the Heathrow area to identify any people who may be responsible for the operation of the drone.

“I want to be clear that the illegal operation of drones at an airfield is extremely dangerous. Under the Aviation Security Act it is an offence to endanger the safety of an aircraft, anyone found guilty of this offence could face a life sentence.

“We are deploying significant resources – both in terms of officers and equipment – to monitor the airspace around Heathrow and to quickly detect and disrupt any illegal drone activity; some of which are as a result of learning from the incidents at Gatwick.

“Following today’s sighting, military assistance has been implemented to support us. However, we will not be discussing in any further detail the range of tactics available to us as this would only serve to potentially undermine their effectiveness.

“We are determined to identify anyone who may have been involved in today’s incident and I would urge anybody who may have information that could assist our investigation to call 101 quoting Heathrow drone incident.

“Similarly, if you see anyone acting suspiciously, including anybody operating a drone or model aircraft in the area around Heathrow, or other airports, then dial 999 immediately.”

The airport confirmed about an hour later that take-offs had resumed. Flight tracker websites showed flights departing from 1811 GMT.

A Reuters witness in a plane on the runway at Heathrow said multiple aircraft were waiting for permission to take off before being later told that things were starting to move .

London’s second busiest airport, Gatwick, was severely disrupted when drones were sighted on three consecutive days in December, resulting in about 1,000 flights being cancelled or diverting and affecting 140,000 passengers.

Gatwick’s drone nightmare – the most disruptive yet at a major airport – exposed a new vulnerability that will be scrutinised by security forces, airlines and airport operators across the world.

The British army was forced to deploy military technology to guard the area around Gatwick, reassuring the airport that it was safe enough to fly.

British Transport Secretary Chris Grayling said on Tuesday the military was preparing to deploy the same equipment at Heathrow.

“We are in contact with Heathrow Airport concerning the drone sighting,” he said.

“I have already spoken to both the Home Secretary and Defence Secretary and the military are preparing to deploy the equipment used at Gatwick at Heathrow quickly should it prove necessary.”

Both airports responded to the Gatwick incident by ordering military-grade anti-drone technology.

Heathrow said it was working closely with authorities including the police and looking at relevant technology to combat the threat of drones.

The airport handled 78 million passengers in 2017 and is the main hub for British Airways. Its busiest routes in terms of passengers numbers are to Dubai and New York-JFK.