Thursday, April 13th, 9:42 (CEST)
A yet unexplained strong pressure shock wave was felt over the town of Sempach, Canton of Lucerne in Switzerland. Residents reported an inaudible thud shook their houses and it made their ears ring. Similar to the pressure when a high speed train enters a tunnel. Witnesses say it felt like a strong “sonic boom” but they did not hear anything. No low flying airplanes could be seen in the blue sky over head. In the town of Sursee, in 8 kilometer distance, a sonic boom was heard but also, no airplane was reported.