A loud bang which sparked a deluge of calls to emergency services across a large part of England was a sonic boom from a Typhoon aircraft, the MoD said.
Mystified residents across the West Midlands, Warwickshire, Oxfordshire, Somerset and Wiltshire reported hearing a loud boom at about 18:10 BST.
The MoD revealed it was from a Typhoon responding to an emergency call.
A Coventry resident called Gary said: "I thought somebody had thrown a brick at the house."
He added: "When I went out there were quite a few people in the street wondering what it was."
A sonic boom is created as an aircraft breaks the sound barrier, causing a high-energy shockwave.
The Ministry of Defence initially said it was investigating what was behind the loud noise, but a spokesman later confirmed it was from one of two RAF Typhoons that had been launched following an emergency call from a helicopter.
Flood of calls
The MoD said the Typhoons, from the Quick Reaction Alert (QRA), based at RAF Coningsby in Lincolnshire, were scrambled and authorised to go supersonic after the small civilian helicopter had emitted an emergency signal.
A spokesman said the frequency was only used when an aircraft was in particular trouble, such as a hijacking.
He said the aircraft were already on their way to the helicopter by the time the helicopter pilot realised he was transmitting on the wrong frequency and switched to the correct one.
"There was no actual threat to the civilian aircraft and they soon rectified their mistake," the MoD spokesman added.
Richard Coglan, who was in Bath at the time of the incident, said: We saw the Eurofighter [Typhoon] circle the helicopter at very slow speed using full thrust just to stay up.
"The helicopter was a small one and totally dwarfed by the typhoon we thought it was filming the Typhoon."
Before the MoD explained the cause, a number of organisations said they were investigating the origin of the sound.
Among them were Warwickshire Fire and Rescue Service, which received a flood of calls, and the British Geological Survey.
Avon and Somerset Police also said they had received reports of a loud bang in the area.
Some of those who heard it said the sound lasted a few seconds.
Tom Sykes, from Highworth, Wiltshire, said: "I was sat at my desk doing some work and it felt like someone had put up a massive bass speaker at my feet.
"I'm sure that they didn't move up in the air but they felt like they were with the vibration. I thought the window had come in."
Terry Organ, from Oldfield Park, Bath, said he saw the Typhoon.
"I thought [the sound] was a commercial airliner and then I thought 'no way'," he said.
"We watched for a while and then we saw this aircraft appear and it was a Typhoon but it was flying amazingly slow and we thought it was going to come down.
'Shook the building'
"It was doing really tight, slow circles and it suddenly put on full power and the noise was unbelievable, it was really blasting it out, and then it moved a bit further on and it did another slow turn.
"My impression was that it was struggling to stay up but then he put on full power again and you just couldn't hear anything.
"The noise was terrific, I imagine you could hear it for miles."
Another person who reported hearing the boom, who gave his name as Dave, from Warwick, described the sound as "like sitting on a hard shoulder and a big lorry going past".
"It shook the building and the windows popped," he added.
It is the second time this year that a sonic boom has been created by a Typhoon aircraft.
In January, the MoD confirmed that a loud noise heard by people across the north of England was caused by an RAF fighter jet breaking the sound barrier.