power to the CVR shut off as the aircraft departed. Some initial speculation suggested that explosives brought down Flight 394. Indeed, the previous December, a bomb had brought down Pan Am Flight 103 over south-western Scotland. In addition, Norwegian Prime Minister Gro Harlem Brundtland had used that particular Partnair aircraft on her campaign trips, leading the Norwegian press to assume that the crash was an assassination attempt. Witnesses of the crash said that they heard a loud noise as they saw the aircraft fall. The fact that the aircraft had disintegrated in the air gave credibility to the bomb theory. Speculation in the press later included a scenario where the plane had been shot down, possibly by the NATO war exercise "Operation Sharp Spear", which took place on the day of the accident flight near the flight path, as investigators had found small traces of high explosives on parts recovered from the sea bed. However, investigators found that the residue was not from a bomb or a warhead, as not enough of it was present. Finn Heimdal, an AIBN investigator, stated that the residue appeared to be more like a contamination than any other possibility. The sea had old munitions as many battles had been fought off the coast of Denmark. Investigators concluded that the aircraft pieces acquired residue from the bottom of the sea or that the traces of explosives were accumulated from contamination before the accident or due to storage. Metallurgist Terry Heaslip of the Canadian company Accident Investigation and Research Inc. examined the aircraft skin from the tail and found signs of overheating, specifically that the skin had been repeatedly flexed, through a phenomenon known as flutter. This caused investigators to further scrutinize the tail of the Convair. Furthermore, the investigation team found that the APU, which was in the tail, generated heat, which melted certain plastic parts, indicating that the APU was operating during the flight even though it normally would not be. The mechanic who had inspected LN-PAA on the day of the accident flight told investigators that one of the aircraft's two main generators had failed and that he was not able to repair the faulty generator. The investigators discovered that the pilots had noted in the flight log that they would operate the APU throughout the flight because two power sources are required for departure. They also discovered that the APU's front mount