From the BBC:
Typhoon sonic boom behind mysterious bang reports - MoD
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 said: "I thought somebody had thrown a brick through the window."
The Ministry of Defence initially said it was investigating what was behind a loud noise in Oxfordshire but a spokesman later confirmed it was from one of two RAF Typhoons that had been launched following an emergency call from a helicopter.
The helicopter had transmitted on the wrong frequency, he said.
Warwickshire Fire and Rescue Service had also said it was looking into what caused the noise, after a flood of calls.
Some of those who heard it said the sound lasted a few seconds.
The British Geological Survey had also said it was investigating the incident.
There were reports of the noise being heard in Bath, Swindon, Coventry, Rugby and Oxford.