Britain on Wednesday scrambled RAF Typhoon fighter jets to escort a Ryanair flight from Lithuania to Britain after a hoax security alert, the defence ministry and airline said, adding that the flight landed safely.

The flight from Kaunas to London Luton was diverted to London's Stansted airport, the British airport designated to deal with major incidents, and there were reports of a sonic boom over eastern England when the fighter jets were deployed.

"The RAF can confirm Quick Reaction Alert Typhoon aircraft were launched this morning from RAF Coningsby to intercept a civilian aircraft. The aircraft was safely escorted to Stansted airport," a spokesman for the Royal Air Force said.

He added the planes had been "authorised to transit at supersonic speed for operational reasons".