The police have confirmed to RTL that the French military was in the middle of an aerial exercise near the Luxembourgish border.
This type of explosion is caused when an aircraft breaks the sound barrier, meaning when an aircraft reaches the speed of sound, i.e. 340 metres per second or 1,230 km/h.
Rest assured, this loud detonation is in no way dangerous. Nonetheless, it is worth noting that the exercise in question is not quite over yet, so there might be similar noises over the next couple of hours.
