A French fighter jet broke the sound barrier as it scrambled to join a commercial jet that had lost contact with air traffic control on Wednesday, causing a sonic boom that reverberated through Paris.
The sonic boom rattled windows in the capital, scattered startled birds and prompted a surge in phone calls to police.
"A Rafale (warplane) based at Saint-Dizier, intervening to assist an airline which had lost contact, was allowed to break the sound barrier to join the airplane in trouble. It broke the sound barrier east of Paris," army spokesman colonel Stephane Spet said in a statement.
It was not immediately clear whether the problem with the commercial jet had been resolved.
In a city already tense since a knife attack outside the former offices of satirical magazine Charlie Hebdo on Friday, the unusually loud blast sent people onto their balconies to see what had caused it. It also prompted intense messaging on social media and a flood of calls to emergency services.
The Paris police prefecture explained what had happened in a statement on Twitter and urged people not to call emergency services about the noise.