Complex sentence: He drops two men from his plane by parachute before crashing, and Doc Daneeka is not among them, but is believed to have been killed in the crash because he had his name put on the flight roster in order to meet the minimum for flight time.
Split into simpler sentences: He drops two men from his plane by parachute before crashing, and Doc Daneeka is not among them. For this reason, Doc Daneeka is believed to have been killed in the crash because he had his name put on the flight roster in order to meet the minimum for flight time.