Investigation Summary
The flight was the second leg of a Singapore-Bangkok-Hong Kong service. While cruising at FL290, a bomb detonated near the starboard wing root, likely positioned under seat 10E or 10F. The suspect, Somchai Chaiyasut, was not on board the aircraft; he had checked his fiancée and daughter onto the flight while remaining in Bangkok. The device was concealed within a suitcase placed under the seat and was likely triggered by a barometric pressure sensor or a timer set for cruise altitude. The explosion created a large hole in the fuselage, causing several seats and passengers to be ejected immediately. Debris from the cabin struck the vertical and horizontal stabilizers, rendering the aircraft uncontrollable. The Convair 880 entered a high-speed descent and disintegrated before impacting a remote, lightly wooded hilltop near Pleiku. Recovery efforts were severely hampered by the ongoing Vietnam War and the presence of Vietcong forces in the vicinity of the crash site.
Final Conclusions
The official inquiry concluded that the crash was caused by the detonation of a high-explosive device within the passenger cabin. Investigators identified a Thai Police Lieutenant, Somchai Chaiyasut, as the primary suspect. He had placed his daughter and fiancée in the seats directly above the blast site and had recently purchased large travel insurance policies naming himself as the beneficiary. Despite evidence suggesting he had acquired C4 explosives and pressured staff to move his family to those specific seats, he was acquitted by a Thai court in 1974.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
Neil Morison, Australian national, aged 42. Company Flight Captain of the CV880 fleet.
First Officer
Lachlan Mackenzie, aged 38.
Second Officer
Leslie Boyer, aged 42.
Flight Engineer
Ken Hickey, aged 36. Company Senior CV880-22M Check Flight Engineer.
Systems & Failure Modes
Fuselage Structure
The detonation created a breach that caused explosive decompression and structural failure of the center section.
Empennage
Secondary damage occurred when cabin debris and seats struck the tail surfaces after being ejected by the blast.
Interesting Facts
- 01The explosion occurred under seat 10E or 10F on the right side of the cabin.
- 02It remains the deadliest aviation incident involving the Convair CV-880 aircraft type.
- 03The suspect, Somchai Chaiyasut, stood to gain $225,000 in insurance payouts.
- 04The device was likely triggered by a barometric sensor, as the explosion occurred shortly after the aircraft reached its cruising altitude.
- 05The aircraft was manufactured in 1962 and had previously served with other operators before Cathay Pacific purchased it in 1967 with 13,295 hours already flown.
- 06At the time of the accident, the airframe had accumulated a total of 29,434 flight hours and 14,892 cycles.
- 07The investigation was a joint effort between South Vietnamese, British, and Hong Kong authorities.
Safety Actions & Advisories
Enhanced Passenger Screening
The bombing contributed to the global push for more rigorous security screening of carry-on items and checked baggage, particularly in Southeast Asia.
Known Controversies & Unanswered Questions
Acquittal of Somchai Chaiyasut
Reference ↗Despite significant circumstantial evidence, including the purchase of large insurance policies and witness testimony regarding C4 explosives, the Thai court acquitted the prime suspect.