Loud bangs were heard across Norfolk as a passenger plane declared an emergency following a "bomb threat".

The AI129 Air India flight from Mumbai to London Heathrow issued the alert while flying over the county.

RAF Eurofighter Typhoon jets from RAF Coningsby in Lincolnshire were scrambled in response to the emergency, letting out a sonic boom as they reached supersonic speed.

A spokesman for the Royal Air Force said: "We can confirm that RAF Quick Reaction Alert Typhoon fighter aircraft from RAF Coningsby were launched this afternoon, to investigate a civilian aircraft.

“Following an uneventful interception the aircraft was released to continue to its original destination under the direction of civilian air traffic control.

"This incident is now being handled under the control of civilian authorities.

“The sonic boom heard across parts of England at lunchtime today was caused by the RAF Typhoon fighter aircraft which were launched from Quick Reaction Alert, the aircraft were authorised to transit at supersonic speed for operational reasons.”

The flight path of the Air India plane over Norfolk (Image: Flight Radar) The bangs were heard just before 12.45pm and were described by one person near Buxton like "two bombs going off above our heads".

Another said: "Just heard an amazingly loud sonic boom in Erpingham.

"All of my neighbours came out to see what it was.

"The whole house shook and the windows vibrated."

Flight AI129 photographed above Norfolk with one of the RAF jets behind itFlight AI129 photographed above Norfolk with one of the RAF jets behind it (Image: Ben Clarke) Norfolk Constabulary issued a statement on Facebook confirming that the loud noise was a sonic boom caused by RAF aircraft and not an explosion.

The flight eventually landed safely at Heathrow Airport.

Indian airlines have been rocked by at least 20 hoax bomb threats in the last three days, prompting a warning from government officials and civil aviation authorities that "very strict action" will be taken.

The majority of the threats have been received on social media forcing emergency diversions, landings and evacuations of flights. 

Air India has been approached for comment.