People in London and Cambridge heard a sonic boom on Tuesday as RAF jets were scrambled to help a private plane.
Residents in Hertfordshire and Essex also reported hearing a loud bang at about 1.19pm.
Many took to social media to describe what they heard, with some saying their homes had shaken due to the force of the shockwave.
One Twitter user wrote: "I thought my next door neighbours were gonna come flying through the wall. So scary! #sonicboom".
A second said: "Sounds like the whole Romford area felt it, whole house shook and you could feel it in the ground".
A third added: "Thought someone from the Primary School had kicked a ball at my window, but it was a sonic boom apparently. Madness."
An RAF spokesperson later confirmed the sound was caused by its aircraft.
"The RAF can confirm Quick Reaction Alert Typhoon aircraft were launched this afternoon from RAF Coningsby to intercept a civilian aircraft that had lost communications.
"Subsequently, communications were re-established, the aircraft was intercepted and safely escorted to Stansted."
Sonic booms are created by the shockwaves created when an object travels through the air faster than the speed of sound.
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