On 25 May 2002, the Boeing 747-209B operating the route disintegrated midair and crashed into the Taiwan Strait, 23 nautical miles (43 km; 26 mi) northeast of the Penghu Islands, 20 minutes after takeoff, killing all 225 people on board.

The in-flight break-up was caused by metal fatigue cracks resulting from improper repairs after a tailstrike to the aircraft 22 years earlier.

[5][11] Chang Chia-juch, the Taiwanese Vice Minister of Transportation and Communications at that time, said that two Cathay Pacific aircraft in the area received B-18255's emergency location-indicator signals.

The first 82 bodies were found floating on the ocean surface of the Taiwan Strait, and were recovered by fishing boats and military vessels.

[1]: 69 The victims were identified by visual identification, personal effects, fingerprints, dental examinations, and through DNA testing.

[1]: 70, 72 At 17:05 local time, a military Lockheed C-130 Hercules aircraft spotted a crashed airliner 23 nautical miles (43 km; 26 mi) northeast of Makung, Penghu Islands.

The items included magazines, documents, luggage, photographs, New Taiwan dollars, aircraft safety cards[17] and a China Airlines-embossed, blood-stained pillow case.

Shortly before the breakup, two of the aircraft's four engines began providing slightly higher thrust, which was later found to have been within the normal ranges of deviation.

[23] The United Daily News stated that some relatives of passengers described the existence of this flight to Hong Kong as being "unnecessary".

The final investigation report found that the accident was the result of fatigue cracking caused by inadequate maintenance after a much earlier tailstrike incident.

[1]: 157–158  According to the SRM, repairs could be made by replacing the entire affected skin or by cutting out the damaged portion and installing a reinforcing doubler plate to restore the structural strength.

[1]: 159 Consequently, after repeated cycles of pressurisation and depressurisation during flight, cracks began to form around the exposed scratches until finally, on 25 May 2002, coincidentally 22 years to the day after the faulty repair was made on the damaged tail, the hull broke open in midair.

A rapid decompression occurred once the crack opened up, causing the separation of the aircraft's fuselage at section 46 (aft of the main wingbox).

On 12 August 1985, 17 years before Flight 611's crash and 7 years after the accident aircraft's repair, Japan Air Lines Flight 123 from Tokyo to Osaka with 524 people on board had crashed when the vertical stabiliser was torn off and the hydraulic systems severed by explosive decompression, leaving only four survivors.

That crash had been attributed to a faulty repair to the rear pressure bulkhead, which had been damaged in 1978 in a tail strike incident.