The National Transportation Safety Board is providing technical support to the Government of Thailand's investigation of a March 3, 2001 explosion and fire that destroyed a 9-year-old Thai Airways International Boeing 737-400 (HS-TDC) that was sitting at a gate at Don Muang International Airport, Bangkok, Thailand. A flight attendant aboard the plane was killed in the blast and subsequent fire, which destroyed the airplane.
The Government of Thailand, in conjunction with the NTSB, is releasing the following information:
On March 22, 2001, Deputy Prime Minister Chavalit Yongchaiyudh related that the investigation is actively pursuing all potential causes for the loss of the airplane and that nothing has been ruled out at this time.
Physical evidence has been found that the center wing tank exploded. The accident occurred at 2:48 p.m. on a day with temperatures in the high 90s Fahrenheit. The initial explosion of the center wing tank was followed 18 minutes later by an explosion in the right wing tank. Air conditioning packs, which are located directly beneath the center wing tank and generate heat when they are running, had been running continuously since the airplane's previous flight, including about 40 minutes on the ground.
Although chemical traces of high energy explosives were initially believed to be present, samples have been submitted to the FBI for confirmation by laboratory equipment that is more sensitive than equipment available in Thailand. Although a final report has not yet been issued, the FBI has found no evidence of high explosives in any of the samples tested to date.
Despite a thorough examination of the wreckage by Thai and American bomb experts, no physical evidence of a bomb has been found to date.
The NTSB has a library of sound signatures recorded from previous flights and tests, including both fuel air explosions and high explosive charges. The recording of the HS-TDC explosion has features that are similar to recorded features of a Philippine Airlines 737-300 center wing fuel tank explosion in May 1990. Neither recording includes a precipitating sound of an initiating explosion that may have ignited the fuel tank.
Many parts from HS-TDC, including fuel pumps and wiring, have been removed and are to be analyzed in laboratories.