A drone flying near Heathrow almost crashed into a passenger jet – raising fears that this year’s must-have Christmas gift could cause a disaster in the skies over Britain.

The remote-controlled device, flown by an unidentified amateur, was spotted by the airliner’s pilot but alarmingly was not detected by air traffic control radars.

The UK Airprox Board, the air safety panel that investigates near misses, gave the incident the highest risk rating of A, meaning there was a ‘serious risk of collision’.

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A drone flying near Heathrow almost crashed into a passenger jet raising fears that this year’s must-have Christmas gift could cause a disaster - the remote-controlled device was flown by an unidentified amateur

It was the first near miss between a passenger jet and an unmanned aircraft at Britain’s biggest airport.

It comes after warnings over the dangers posed to passenger planes by recreational drones flown by amateurs.

They are expected to be a best-seller this Christmas, with models as cheap as £35 being snapped up.

Sales have risen rapidly – around 2,000 a month are being bought – and electronics retailer Maplin said they are currently one of its biggest sellers.

The most sophisticated designs cost up to £3,000.

A plane had a near miss with drone as it landed at Heathrow (pictured) on July 22 in the first recorded incident

They can include cameras and are usually used for recreational purposes – although increasingly they are being considered for commercial uses, such as carrying deliveries and monitoring farmers’ crops.

The Airprox Board will publish a report later this week into the Heathrow incident, which involved an Airbus A320 that can carry up to 180 passengers.

The jet was flying at an altitude of 700ft on the afternoon of July 22 this year when the pilot spotted the drone. He reported the near miss and an inquiry was launched by the board.

Worryingly, investigators were unable to identify the drone and it disappeared after the sighting.

It is the latest in a series of incidents involving unmanned planes.

In May, the pilot of a 74-seat plane reported that a quadcopter drone flew within 80ft as he was approaching Southend airport and in December 2012, the crew of a Boeing 777 coming in to land at Gatwick said they saw ‘two white or silver discs’.

Drones (file picture) are priced from just £35 and sales have jumped thanks to extra pre-Christmas demand

In April this year, the owner of a remote-controlled plane was ordered to pay £4,340 in fines and costs after his machine crashed in a no-fly zone near a shipyard in Cumbria for defence company BAE Systems, where nuclear submarines were being built.

The British Airline Pilots Association (Balpa) has demanded better protection for the public against the risk of drones.

There are currently few rules on operating drones. But Balpa wants them to meet the same safety standards as piloted aircraft, including only being flown by operators with pilot-equivalent training.

Balpa general secretary Jim McAuslan said: ‘The UK should become a “safe drone zone” so we can make the most of the major business and leisure opportunities offered by remotely piloted aircraft, while protecting passengers, pilots and residents.’

The device was spotted by the pilot but was not detected by air traffic control radars at Heathrow (pictured)

He added: ‘The technology is developing quickly and we could see remote aircraft the same size as a Boeing 737 being operated commercially in our skies within ten years.’

In October, intelligence experts warned of the misuse of drones and called for ‘urgent’ measures to safeguard British airspace to cope with commercial use, which is expected to be more widespread by 2035.

Their research for a University of Birmingham report said that the ‘hazards presented by inadvertent or accidental misuse of [drones], or the consequences of their malfunctioning, are becoming better understood’.