Aero OY flight 217, a Douglas DC-3, crashed while on approach to Mariehamn Airport, Finland, killing 22 occupants; 3 survived the accident. Flight 217 operated on a Helsinki-Turku-Mariehamn flight and left Turku (TKU) at 16:20 GMT. The last leg of the flight was carried out at an altitude of 2000 feet. At 16:57 the crew reported over the MAR NDB on the inbound track to runway 20. During the approach the aircraft struck trees in a nearly horizontal attitude 1470 m before the threshold of the runway. The plane flipped over and caught fire. 22 occupants including pilot Pekka Marttinen, co-pilot Pekka Yli-Niemi and former Aero OY pilot Antti Joensuu traveling as passenger in the cockpit. Three survived the accident, flight attendant Marianne Kullberg and two passengers. PROBABLE CAUSE: “The Board considered that the ultimate cause of the accident was the pilot’s misconception of his altitude. It was impossible to determine whether this was due to a wrong indication of the altimeter or human error. The defect, found in the pilot-in-command’s altimeter, was regarded however as sufficient to have brought a wrong indication of the altitude which the pilot could not foresee. The cause of the accident was therefore established as follows: As a result of a wrong indication of the aircraft’s pilot’s altimeter during an instrument approach carried out in weather conditions worse than the weather approved for runway 20 at Mariehamn, the aircraft came below the safe flying altitude and hit trees on the approach line.”