Complex sentence: The officials concluded that the plane was completely capable of flying, and that the probable cause for the accident was a pilot error when turning to the left, although it was possible that one passenger was interrupting the pilots based on his body's location.
Split into simpler sentences: The officials concluded that the plane had been completely airworthy, and that the probable cause of the accident was a pilot error when turning to the left. The possibility was noted that one passenger had been interrupting the pilots based on his body's location.