Fire crews were mobilised following reports of loud explosions in the Midlands.
But the two bangs heard around Northampton and Brackley were caused by Typhoon jets which had been scrambled from an RAF base in Lincolnshire to identify an unresponsive aircraft.
People posted on social media about feeling a "huge explosion" in the area at around 3.50pm on Friday.
James Simpson wrote on Twitter: "Just heard and felt a huge explosion in Northampton. Felt in Round Spinney Industrial Estate, friend in Billing had the same!"
Simon Crow tweeted: "Did anyone else hear the very loud bang/explosion about 15.55? Made the house shake and I jumped out my skin. Was heard across Northampton."
Northamptonshire Fire and Rescue said crews were mobilised to reports of the explosions - but it was later confirmed the noise was caused by "two jets flying over the area creating a sonic boom".
A Ministry of Defence spokesman said: "Quick reaction alert Typhoon aircraft were launched today from RAF Coningsby to identify an unresponsive civilian aircraft.
"Communications were re-established and the aircraft has been safely escorted to Cardiff airport."