The co-pilot requested free flying altitude from the air traffic control, which was permitted.

[2]: 17 Shortly after the flight's last radio contact with air traffic control, in which the pilots confirmed the weather report and said that they would be at the Seppä non-directional radio beacon in a few minutes, Flight 311 was starting to prepare for landing by descending below 50 metres (160 ft).

The investigation report concluded that this was unlikely in the flying conditions, and an intact wing that had separated from the main wreckage did not have any ice on it.

[2]: 20 According to the report by the AIB, neither the pilot, Captain Lars Hattinen, nor the co-pilot, First Officer Veikko Halme, were in a fit state to fly.

[2]: 15  In all, Hattinen, Halme, and the possible cockpit visitor had drunk sixteen bottles of beer, seven gin grogs, and 900 grams of cognac from 21:50 to 02:00.

[2]: 14 [3] Both the International Civil Aviation Organization's treaty and the pilots' personal job contracts barred intoxication while in command of a plane—provisions that Hattinen and Halme ignored.

[2]: 15  In addition, as captain Hattinen was a World War II veteran pilot and a former fighter ace having six aerial victories, he was used to taking large risks before and during flights.