The report indicated that on 7 February 1980, the aircraft used on the flight had a tailstrike accident while landing in Hong Kong.[21] Part of the plane's tail scraped along the runway for several hundred feet. The aircraft was de-pressurized, ferried back to Taiwan on the same day, and a temporary repair done the day after. A more permanent repair was conducted by a team from China Airlines from 23 May through 26 May 1980. However, the permanent repair of the tail strike was not carried out in accordance with the Boeing Structural Repair Manual (SRM). The area of damaged skin in Section 46 was not removed (trimmed) and the repair doubler plate that was supposed to cover in excess of 30% of the damaged area did not extend beyond the entire damaged area enough to restore the overall structural strength.
Consequently, after repeated cycles of depressurization and pressurization during flight, the weakened hull gradually started to crack and finally broke open in mid-flight on 25 May 2002, exactly 22 years to the day after the faulty repair was made upon the damaged tail. An explosive decompression of the aircraft occurred once the crack opened up, causing the complete disintegration of the aircraft in mid-air.[4]
This was not the first time that a plane had crashed because of a faulty repair following a tailstrike. On 12 August 1985, 17 years before the Flight 611 crash and five years after the accident aircraft's repair, Japan Airlines Flight 123 had crashed when the vertical stabilizer was torn off and the hydraulic systems severed by explosive decompression, killing 520 of the 524 people on board the aircraft. That crash had been attributed to a faulty repair to the rear pressure bulkhead, which had been damaged in 1978 in a tailstrike incident.[22] In both crashes, the faulty repair had been an incorrectly installed doubler plate that was not installed according to Boeing standards.
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