of aircraft was a well-known phenomenon at the time of the accident. From 1985 onward, McDonnell Douglas gave extensive information, including several "All Operators Letters" that dealt with the clear ice problem. In the "All Operators Letter" of 14 October 1986, operators were informed of how the Finnish airline Finnair had solved the problem of discovering clear ice. In 1988 and 1989, McDonnell Douglas arranged "Theme Conferences" dealing with clear ice formation. SAS took part in these conferences. On 26 October 1991, SAS distributed a "Flight Deck Bulletin/Winterization" to all pilots. It stated: "It is the Pilot-in-Charge's responsibility to check the aircraft for any ice or snow that may affect performance" and in the section "Clear Ice", it noted " [a]lthough the awareness within Line Maintenance is mostly good, the responsibility again rests with the Pilot-in-Charge that the aircraft is physically checked by means of a hands-on check on the upper side of the wing. A visual check from a ladder or when standing on the ground is not enough". Another contribution to the accident was insufficient training of the crew; they were not trained in restoring engine operation after they repeatedly surged. There was no simulator or other training on the engine surging problem. Secondly, they were not informed about a pre-installed automatic thrust system (automatic thrust restoration or ATR). The reason for this lapse of information was that there was no knowledge of ATR within SAS. Nonetheless, ATR was described in manuals by the aircraft manufacturer, which every operator is obliged to know. Even though the system was developed for use in procedures not applied by SAS, a sufficiently careful study of the manuals should have led to SAS noting the system and training its pilots in its function. The conclusion of the official accident report stated: "The accident was caused by SAS' instructions and routines being inadequate to ensure that clear ice was removed from the wings of the aircraft prior to takeoff. Hence the aircraft took off with clear ice on the wings. In connection with liftoff, the clear ice loosened and was ingested by the engines. The ice caused damage to the engine fan stages, which led to engine surges. The surges destroyed the engines. Contributory causes were: The pilots were not trained to identify and eliminate engine surging. ATR, which was unknown within SAS, was activated and increased the engine power without the pilots'