A French military plane broke the sound barrier and startled Parisians after it was scrambled to aid two commercial aircraft which had lost radio contact.

Players at the French Open Grand Slam tennis tournament paused play in astonishment. People in Paris have been on edge following last week’s knife attack, deemed a terrorist act by authorities.

This time French police hastened to urge residents fearful of an explosion not to call emergency services. “A Rafale, carrying out an intervention to assist an aircraft that had lost contact, was authorised to break the sound barrier to reach the aircraft in difficulty,” an Air Force spokesman told AFP news agency.

A sonic boom is the noise linked to shock waves created when an object travels through air faster than the speed of sound. It can sound similar to explosions or thunder.

The sound barrier was broken in the east of Paris, said army spokesman Colonel Stephane Spet, according to Reuters news agency. Communication with both aircraft was restored shortly after the boom, France’s civil aviation authority told AFP.

One plane was a Falcon 50 operated by a Brazilian company flying between Cape Verde and Brussels, and the other was travelling between French cities Brives and Saint-Brieuc and operated by Amelia airline. The loud noise shook windows around the city and suburbs of Paris and caused alarm to residents.

At Roland Garros, tennis players Stan Wawrinka and Dominik Koepfer paused their game as the sound echoed around the court. Another player, Ukraine’s Elina Svitolina, commented: “Yeah, I heard it. I was a bit worried because I thought something bad happened.” “I looked at the chair umpire. He was little bit shocked as well because you never know these days what can happen, what’s going on.” “A very loud noise was heard in Paris and in the Paris region. It was not an explosion, it was a fighter jet breaking the sound barrier,” French police wrote on Twitter on Tuesday lunchtime, urging people not to call.

Last Friday, a man with a knife cleaver attacked and wounded two people in the street outside the former office of controversial satirical magazine Charlie Hebdo.
It came as a high-profile trial was under way of 14 people accused of helping two jihadists carry out the 2015 attack on Charlie Hebdo, in which 12 people were killed.

On Monday seven people were detained in connection with last week’s attack.

An inquiry will be launched into why the aircraft lost radio contact, French authorities said on Tuesday.