Investigation Summary
Flight 739 was a Military Air Transport Service (MATS) charter transporting 93 U.S. Army members, primarily highly trained electronics and communications specialists, to South Vietnam. While the official manifest listed them as specialists, many historians and secondary sources identify them as jungle-trained Army Rangers. The flight had completed three successful refueling stops at Honolulu, Wake Island, and Guam. The departure from Honolulu was notably delayed by 30 minutes due to crew complaints regarding inadequate rest facilities. Shortly after departing Guam for Clark Air Base in the Philippines, the crew requested a climb to 18,000 feet. The last routine radio contact occurred at 14:22 GMT. When the aircraft failed to make its 15:30 position report, an emergency was declared. The search effort involved 1,300 personnel, 48 aircraft, and 8 ships, covering more than 200,000 square miles. The only lead was a report from the tanker S.S. T. L. Lenzen, which observed a 'luminous' explosion with two falling objects at the exact time and location the aircraft was expected for its 15:30 report. Because no physical evidence was found, the Civil Aeronautics Board could not determine a cause, leaving the disappearance as one of the greatest mysteries of the Cold War era.
Final Conclusions
The Civil Aeronautics Board concluded that the aircraft likely suffered an in-flight explosion, as evidenced by the S.S. T. L. Lenzen's observations. However, due to the total lack of wreckage, the board was unable to determine the origin of the explosion, whether it was mechanical, accidental, or the result of sabotage.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Ignition System
Minor maintenance was required on engines 1 and 3 at Honolulu and Wake Island to replace coils, leads, and plugs.
Air Conditioning System
Checked at Honolulu at the flight engineer's request; no discrepancies were found.
Interesting Facts
- 01The flight was carrying 93 U.S. Army Rangers who were hand-picked communications specialists.
- 02The search operation was one of the largest ever conducted in the Pacific, covering more than 200,000 square miles.
- 03The S.S. T. L. Lenzen tanker crew saw a radar target at the same bearing as the explosion, but found no debris upon arrival.
- 04Minor maintenance was performed on engines 1 and 3 during earlier stops in Honolulu and Wake Island.
- 05The aircraft was only five years old and had a total of 17,224 airframe hours.
- 06Investigators found that the flight line and ramp areas at the refueling stops were not secure, allowing potential unauthorized access.
Known Controversies & Unanswered Questions
Nature of the Mission
Reference ↗Speculation exists regarding the secret nature of the Army Rangers' mission, with theories ranging from CIA support to specialized reconnaissance, though the official manifest listed them as communications specialists.
Sabotage Allegations
Reference ↗Due to the sudden disappearance and the military importance of the passengers, sabotage was investigated, but the CAB found no evidence to support or refute the theory.