The co-pilot of OceanicFlight 815 almost certainly died in the impact when the cockpit and first class section crashed. He was seated at the cockpit during the time of the crash. It is not known how he died but it is likely he died during the collision of the cockpit and first class section. His body fell out of the cockpit in "Pilot, Part 1", as Jack, Charlie and Kate entered it looking for a radio which means that he was not in his seat after the crash of the front section of the plane. It is not known if his body was buried by the middle section survivors by the cockpit and first class section but it is likely that his body was left there after the Monster killed the pilot.