Complex sentence: This sort of dangerous stunt was fairly common during the early era of loosely regulated flying in the 1920s but the train's passengers included ranking officers coming to March Field to participate in the graduation ceremonies and Mantz was subsequently dismissed from the Army.
Split into simpler sentences: This sort of dangerous stunt was fairly common during the early era of loosely regulated flying in the 1920s. The train's passengers included ranking officers coming to March Field to participate in the graduation ceremonies and Mantz was subsequently dismissed from the Army.