Complex sentence: For reasons never explained, pilot Frank Atkinson and co-pilot Marion Ewing took the wrong airplane for the flight, with the plane that they were supposed to fly being a DC-3 that was certified to carry thirty-two passengers.
Split into simpler sentences: For reasons never explained, pilot Frank Atkinson and co-pilot Marion Ewing took the wrong airplane for the flight. The plane that they were supposed to fly was a DC-3 that was certified to carry thirty-two passengers.