Sonic booms were heard by residents on the ground
British RAF Typhoon jets were scrambled to intercept a private plane over the Midlands region there on Friday afternoon, with locals saying they were shaken by two "almighty" sonic booms.
The booms were described by some on the ground as "huge explosions" - with fire crews even being sent out to investigate the area around Northampton and Brackley.
They were told to stand down after it was confirmed the noise was caused by the jets speeding over the area.
It is understood that the plane was a private jet on its way to Dublin.
Some locals posted on social media, worried about the cause of the booms, with Linda Sgoluppi tweeting: "Anyone know what the almighty bang about 15 minutes ago was over Northampton area? #Bang".
Laura later posted: "Here's me blaming the boiler when it was a sonic boom the first time around".
A UK 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".
A sonic boom occurs when an aircraft flies faster than the speed of sound and is usually heard at around 760mph.