Fairchild SA-227-AC, Carlsbad, N.M., Aug. 31, 2008–The NTSB determined that the McNeely Charter Service Metro turboprop lost its door in flight because the door failed to remain secure for undetermined reasons. The captain, a 12,250-hour ATP with 5,200 hours in make and model, said he secured the door normally but couldn’t remember whether he saw that it was closed. En route, there were variations in the airplane’s cabin pressure and the pilot found an air leak from the entrance door area. When the airplane ran into turbulence moments later, the door flew off, causing substantial damage to the fuselage. The pilot declared an emergency and landed at the nearest suitable airport. The door was not found, and an exact cause of the failure could not be determined. The sole-occupant pilot was not injured.