Cathay Pacific Flight 700Z

Investigation

The wreckage was located by a United States Army helicopter in "lightly wooded" terrain on a remote hilltop near Pleiku, still burning, not long after Saigon ATC lost contact. Although two bodies were retrieved almost immediately, the presence of hostile Vietcong forces nearby made it very difficult to examine the wreckage in depth. South Vietnamese soldiers were drafted in to search for the wreckage and secure the crash site. It was reported that before the area was secured, local villagers and Viet Cong had gone through the wreckage looking for valuables. The South Vietnamese Civil Aviation Department, the Thai government, and Cathay Pacific Airways each had their own investigations. Two British men, Vernon Clancy and Eric Newton, went to the location to get information about the crash. Newton was the primary person investigating aviation accidents at the Civil Aviation Authority, while Clancy used to be a part of the Royal Armament Research and Development Establishment.

The spread of debris suggested that the airplane had broken into three large sections, with the breakpoints almost exactly along the front and rear of the wingbox, prior to hitting the ground, and the relative closeness of these sections suggested that this breakup had occurred at a low altitude. Other debris, including two engines and the horizontal stabilizer, could be seen further away from helicopters, but could not be reached on foot due to war activity. The rear section of the aircraft was later found impaled on a tree with the bodies of thirteen passengers and two cabin crew members still inside while the middle section was found to have exploded on impact with the ground. The aircraft's flight data recorder was recovered and read; it showed that the airplane was flying on course at 29,000 ft at a speed of 310 kn until 05:59 GMT (12:59 local time), at which point the recorded data became nonsensical for 30 seconds before stopping entirely. The aircraft was not equipped with a cockpit voice recorder. The detonation occurred after 64 minutes and 2 seconds in the air.

Upon examining the available debris, it soon became clear that the aircraft had suffered some sort of structural problem and loss of control at cruising altitude, and that the low-altitude breakup was caused by the overstressing of the airplane during an uncontrolled descent. Debris from the centre fuselage and right wing root showed signs of explosive "splash", and the number 3 fuel tank showed signs that it had ruptured prior to the low-altitude breakup inferred from the wreckage distribution. The vertical stabilizer showed signs that it had been struck by "at least one body and possibly some seats", and the horizontal stabilizer also showed signs of being damaged by debris in the air. Many bodies were not recovered, possibly because they had been ejected very early in this sequence. An investigator working at the crash site summarised that the plane suffered an explosive decompression around 1pm local time. According to Young, the cabin crew were found wearing serving jackets and aprons, and so "One can assume" that the crew were serving lunch at the time of the in-flight breakup. The passengers standing in the aisle or queuing for the lavatory and cabin crew members overseeing the meal service were sucked out of the aircraft as it disintegrated.

Without being able to better examine the wreckage, and lacking valid flight data from the final moments of the flight, it is not known what exactly happened after 05:59 GMT. Investigators concluded that apparently some sort of explosive device, likely located within the passenger cabin near the right wingbox, detonated at that time, causing unknown but catastrophic damage to the aircraft, including but not limited to the damage found on the horizontal and vertical stabilizer. The aircraft likely descended rapidly in an "erratic" manner. At an undetermined point in this descent, the horizontal stabilizer separated from the airplane entirely, and eventually the fuselage broke into the three sections initially found by searchers.

According to McBeth, experts had theorised that the person bombing the aircraft intended for it to fall into the ocean, which would make extracting information from the debris more difficult. McBeth said, "The Cathay Pacific bomber erred in his timing." The aircraft would have began flying over water six minutes after the time the bomb detonated.