| Occurrence Type: | Accident |
| Thai Airways International Flight 620 | |
| Date: | 26 October 1986 |
| Type: | Accidental hand grenade explosion |
| Site: | Tosa Bay, while en-route Manila to Osaka |
| Aircraft Name: | Sukhothai |
| Aircraft Type: | Airbus A300B4-601 |
| Origin: | Don Mueang International Airport, Bangkok, Thailand |
| Stopover: | Ninoy Aquino International Airport Manila, Philippines |
| Destination: | Osaka International Airport, Osaka, Japan |
| Operator: | Thai Airways International |
| Tail Number: | HS-TAE |
| Passengers: | 233 |
| Crew: | 14 |
| Fatalities: | 0 |
| Injuries: | 109 |
| Survivors: | 247 (all) |
Thai Airways International Flight 620 was a scheduled Thai Airways International passenger flight from Bangkok to Osaka via Manila. The Airbus A300B4-601 aircraft, originating in Bangkok, suffered an explosion mid-flight. The aircraft was later repaired and there were no fatalities. The cause was a hand grenade brought onto the plane by a Japanese gangster of the Yamaguchi-gumi. 109 of the 239 people on board were injured. The aircraft descended rapidly and was able to land safely at Osaka.[1] [2] [3] [4] [5] [6] [7] [8]
At around 8PM of October 26, 1986, Thai Airways International Flight 620 (Airbus A300-600, Registration HS-TAE) was cruising above Tosa Bay off the coast of Kochi Prefecture, carrying 14 crews and 233 passengers, when the rear of the aircraft suddenly suffered an explosion, resulting in rapid decompression and damage to the rear pressure bulkhead, severing two of the three hydraulic pipes. As a result, the aircraft veered off course for about 100 kilometers and into restricted air space of the Japan Air Self Defense Force, as well as going into a dutch roll at one point, but the aircraft managed to make an emergency landing at Osaka Itami Airport at 8:40 PM.[9] [10]
As a result of the explosion and the aircraft's violent turbulence, a total of 109 passengers and crew suffered injuries, with 14 of them suffering severe injuries.[11]
Initially, it was believed that, like Japan Air Lines Flight 123 a year before, some sort of a mechanical problem was to blame for the incident.[12] While the aircraft was delivered less than three weeks before the incident, the pressurization devices were having issues in the week leading up to the incident, with reports being made that warning lights were turning on.
However, it was quickly revealed after the aircraft was examined by the that the explosion was caused by some sort of an explosive that was brought in, rather than the aircraft itself.[13] Ultimately, a 43-year-old yakuza of the Yamaguchi-gumi admitted to smuggling the hand grenade into the aircraft. The yakuza stated that he "accidentally pulled the safety pin off in the toilet that was at the rear left area of the toilet" and that "he tried to put the pin back in, but it didn't work, so he left it behind in the toilet and let it blow up".[14]
The yakuza who brought in the hand grenade was not arrested until after he was discharged from the hospital, because the man had suffered severe burns all over his body as oil from a broken hydraulic pipe poured over him during the incident.
The aircraft involved, HS-TAE, was delivered less than three weeks before the incident on October 9.