Complex sentence: It was tested on Lake Maggiore in 1921: its brief maiden flight took place on February 12 or March 2; shortly after the second takeoff, on March 4, the aircraft crashed on the water surface and broke up upon impact.
Split into simpler sentences: It was tested on Lake Maggiore in 1921: its brief maiden flight took place on February 12 or March 2. Its second flight was March 4; shortly after takeoff, the aircraft crashed on the water surface and broke up upon impact.