that two months before the crash, the vibrations stopped for two weeks, from immediately after the aircraft received a major overhaul in Canada by the airline's previous owner. During the Canadian company's test flights of the aircraft and its first several passenger flights for Partnair, the FDR recorded almost no abnormal vibrations. A review of the maintenance records of the aircraft revealed that during the overhaul, the mechanic discovered wear on one of the four bolts that held the vertical fin and fuselage together and replaced it. The vibrations stopped after the one bolt, with its associated sleeves, was replaced. When the vibrations later returned, they steadily increased until the accident flight. After investigators recovered all four bolts, sleeves, and pins, they found that the bolt and parts installed by the Canadian firm were properly approved equipment, but the other three bolts and their parts were counterfeit and were incorrectly heat-treated during manufacture. Those bolts each could bear only about 60% of their intended breaking strength, making them less than practical to use on the aircraft. The fake bolts and sleeves wore down excessively, causing the tail to vibrate for 16 completed flights and the accident flight. The investigators concluded that eventually, the broken APU mount and the weak bolts holding the tail meant that both pieces were vibrating, and these vibrations reached the same frequency and went into resonance, where the force of multiple same-frequency vibrations add to that of one another and create one large vibration. Thus, the tail's vibration increased in amplitude until it failed and broke off. Aftermath As a result of the crash being caused by fraudulent parts, the United States introduced reforms to the aircraft parts industry, and there was a period of more aggressive enforcement against counterfeit parts providers. Mary Schiavo, the Inspector General of the United States Department of Transportation from 1990 to 1996, oversaw investigations leading to over 150 criminal convictions and over $47 million in restitutions and fines under the Suspected Unapproved Parts (SUP) program. Nevertheless, the SUP program was canceled in 2007. Dramatization The crash was featured in season seven of the internationally distributed Canadian made documentary series, Mayday, in the episode entitled "Blown Apart". Maps References External links AIB-Norway's report on the accident (English version) (Archive) AIB-Norway's report on the accident (Archive) Article by Snorre Sklet on major Norwegian disasters (see page 139, PDF file, article is in