A foreign aircraft intercepted over Kent's skies by military jets yesterday was 'very close' to being shot down, an aviation expert has confirmed.

A huge boom shook West Kent after Typhoon fighter jets from RAF Coningsby broke the sound barrier as they raced to intercept a Russian-built Latvian cargo plane which had failed to respond to numerous attempted communications.

It was today revealed the foreign plane would have been shot down if its crew had not responded to the chilling final warning issued by one of the RAF pilots.

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Aviation expert Chris Yates said: "This was a very serious incident, the short answer is the plane came very close to being shot down. The audio of the RAF pilot warning the cargo plane's crew was the final warning they would have received.

"At the point of take off the pilots have all the authorization they need to take a pot shot at the plane.

"If the Latvian aircraft had not responded at that point it would have been shot down."

After contact was finally made the cargo plane was escorted to Stansted Airport, in Essex, by the RAF Typhoons.

On landing at 5.17pm, police surrounded the plane and three people were reprimanded for losing contact with air traffic control, causing a national emergency response.

Emergency services were flooded with calls from anxious residents who reported a deafening bang across Kent just before 4.45pm.

The sound was confirmed by Kent Police as a sonic boom created by the RAF fighter planes which scrambled to intercept the aircraft.

Initial reports suggested an unidentified plane was warned it could be shot down. It's now believed to be a Russian-made Latvian cargo plane carrying car parts.

An RAF spokesman said: “Typhoon aircraft were launched this afternoon from RAF Coningsby to intercept a civilian aircraft south of London which was causing concern to air traffic control authorities. The aircraft was safely escorted to London Stansted.

"To fulfill their quick reaction role the Typhoons were cleared to travel at supersonic speed, any noise disturbance as a result of this is regretted. Essex Police now have the lead.”

The Latvian company, RAF Avia, which the plane is registered to transports a variety of items including dangerous and radioactive material, according to its website.

It's believed the plane failed to connect to the correct radio channel, and the RAF fighter planes were carrying out standard procedure when a plane loses air traffic control.

Stansted Airport later confirmed that an unknown aircraft was escorted by RAF aircraft and landed at the Essex airfield at 5.15pm.

It has now been identified as an Antonov, a Russian-built cargo plane. Police conducted checks on the aircraft, and the airport remained open as usual.

The plane continued its journey to Birmingham after the being checked over by authorities.

Some residents reported that the sonic boom shook their house, others said it could be heard in towns as far as Sidcup and Swanley.

Kent Police were quick to confirm that the noise was created by RAF activity over the county after being deluged with calls from anxious residents.

Jan Redman tweeted: "Very loud explosion in Sevenoaks area - our house shook - what was it?"

Others feared it may have been a bomb exploding in the county.

This CCTV footage provided by Iain Dodsworth captures video and audio of the boom last night.

A householder in Greenhithe said he heard a huge bang as if two lorries had crashed outside his house.

But when he looked out of the window, all he saw were similarly mystified people trying to find the source of the explosion.

Hannah Spencer, from Coxheath in Maidstone said the bang shook her entire house, she added: "Windows were rattling and vibrating I thought it was thunder at first."

One resident said they felt as if their loft was falling down - while others said they had never heard a sound so big.

London Ambulance Service confirmed it sent crews to Bromley after reports of an explosion but cancelled the call after nothing was found.

The RAF has issued a formal apology. It reads: "Apologies if we startled you during the successful intercept this afternoon - we only go supersonic over land when absolutely necessary."

RAF Coningsby,, in Lincolnshire, has been a frontline station in the defence of the United Kingdom for more than 70 years and is home to 3,000 RAF personnel.

It is one of two stations that defend the skies over Britain. The other station is RAF Leuchars in Fife, Scotland.

Both provide Quick Reaction Alert (QRA) and scramble their fighter jets within minutes to meet or intercept aircraft which give cause for concern.

In an interview with the Ministry of Defence RAF Flight Lieutenant and Typhoon pilot Noel Rees said: “At the start of the scaled QRA response, air traffic controllers might see on their screens an aircraft behaving erratically, not responding to their radio calls, or note that it’s transmitting a distress signal through its transponder.

“Rather than scramble Typhoons at the first hint of something abnormal, a controller has the option to put them on a higher level of alert, ‘a call to cockpit’. In this scenario the pilot races to the plane and gets ready to take off. From this posture a controller can monitor a situation knowing that a scramble can be conducted in moments.”