Cops are investigating after Derby locals reported feeling an explosion for miles.
Many have speculated it was a sonic boom felt by so many people.
Others claim the testing of the Bloodhound Land Speed Record.
While some jokers said the explosion could have been down to outgoing Derby County manager Frank Lampard dropping his wallet.
Derby Cops tweeted: “We are currently taking large reports of a loud bang in the Ilkeston/Derby area. This is currently under investigation and if you have any information regarding this please dial 999 straight away!”
A witness told of the terror when the blast was felt.
They told Derby Live: “There have been a couple of explosion type bangs in Spondon. Apparently the whole of Asda stopped in silence.
“The bus I was on shook. Everyone on the bus is talking about it.”
Derby resident Hannah Watts added: “The bang was really loud – it scared my cat enough to make him run and hide under my bed.
“It rumbled the ground.”
Police later confirmed the blast was a sonic boom, caused by a passing Royal Air Force jet.
They tweeted: “If you heard a loud bang over Derbyshire today, this was a result of an RAF jet passing over that caused a sonic boom.”
RAF typhoon jets were scrambled to intercept an Air India flight due to a bomb threat, which was grounded at Stansted.
An RAF spokesman said: “The RAF can confirm QRA Typhoons were launched this morning from RAF Coningsby to intercept a civilian aircraft.
“The aircraft was escorted to Stansted.
“The Typhoons transited at supersonic speed for operational reasons; any inconvenience caused to local residents is regretted.”