A sonic boom was heard in parts of England after two RAF fighter jets scrambled to intercept a private aircraft.
The Typhoon jets took off from RAF Coningsby in Lincolnshire after a San Marino-registered plane lost contact with air traffic control over Cambridgeshire, the RAF said.
The loud bang, heard at around 11.35am on Friday, was reported across southern Essex, Cambridgeshire, Suffolk, Kent and parts of London.
Some residents described the sound as a “vacuum-style” bang, while others said it shook houses and rattled doors.
The civilian aircraft was later escorted to Stansted Airport, the RAF confirmed, and Essex Police said there was “nothing of concern” once it had landed.
An RAF spokesperson said communications with the aircraft were re-established before it landed safely, and the Typhoons returned to base.
What is a sonic boom?
According to the US Air Force, a sonic boom is an impulsive noise, similar to thunder, created when an object travels faster than the speed of sound, which is around 750mph.
As an aircraft breaks this barrier, it generates shockwaves that cause a rapid build-up and release of air pressure, producing the loud bang heard on the ground.
These shockwaves form continuously along the aircraft’s flight path and can be influenced by manoeuvres, altitude and weather conditions, according to the US Air Force.
At higher altitudes, the overpressure, and therefore the strength of the boom, is lower, but the area affected is wider.
Can a sonic boom cause damage?
The US Air Force says most community exposure to a sonic boom produces less than half a kilogram per square foot of pressure. This is well below the level likely to cause structural damage, it said.
In some rare cases, strong booms may shatter glass, but most homes in good condition can withstand the pressure created by the boom.
Most fighter jets produce booms lasting less than a second, with intensity felt greatest directly under their flight path.
Types of sonic boom
There are two main categories of sonic booms, according to the US Air Force:
- A N-wave: generated during steady flight and has a single pressure peak before returning to normal levels.
- A U-wave: caused by manoeuvres such as turns or dives and has amplified pressure peaks at both the front and rear of the wave, although these affect a smaller area.
What is an RAF Typhoon jet?
Typhoon jets can reach speeds of up to 1,381mph, almost twice the speed of sound, and can operate at altitudes up to 55,000ft (17,000m).
Each aircraft costs around £120m, and as of February 2023, the RAF operated 137 Typhoons across seven squadrons.
They are supported by Voyager refuelling aircraft, which can carry 111,000kg of fuel and enable Typhoons to remain airborne over long distances.
