On the 16th of March, 1962, a Lockheed Super Constellation airliner disappeared over the Pacific.

The Flying Tiger Line was the first scheduled cargo airline in the US. It was named after the Flying Tigers fighter unit, a World War II group of pilots from the US Army, Navy and Marine Corps whose shark-faced fighter jets became an iconic symbol of World War II combat aircraft.

The Flying Tiger Line started after the war, with ten former Flying Tiger pilots, flying freighters they purchased as war surplus from the US Navy. The pilots and two ground crew provided half of the initial investment; oil tycoon Samuel B. Mosher funded the rest. They offered cargo services throughout the US and carried supplies across the Pacific to US Troops during the occupation of Japan.

Two decades later, Flying Tiger Line flight 739 was a charter flight operated by Flying Tiger Line on behalf of the Military Air Transport Service. The aircraft was Lockheed model 1049H registered as 6921C. The Lockheed Super Constellation transport airliner required four crew and could carry 47-106 passengers.

Flight 739 was scheduled with two flight crews (Captain, First Officer, Second Officer, two Flight Engineers and two Navigators), four cabin crew and 96 passengers for a flight from Travis Air Force Base in California to Saigon in South Vietnam, with refuelling stops in Honolulu, Wake Island, Guam, and the Philippines.

Ninety-three of the passengers were jungle-trained Army Rangers, primarily highly trained electronics and communications specialists. The other three were members of the armed forces of Vietnam. The flight crew, five men and four women, were all civilians.

The cargo consisted only of passenger baggage: personal articles and clothing.

The flight departed Travis Air Force Base at 05:45 GMT on the 14th of March 1962 and proceeded normally for the next twelve hours, arriving in Honolulu at 17:44 GMT. All times are given in GMT except where otherwise noted.

The aircraft went through minor maintenance. No issues of concern were found. The departure flight was delayed by half an hour after the cabin crew raised concerns about the crew rest facilities on the aircraft. The issues were resolved and the flight departed Honolulu at 20:40.

The next leg proceeded normally and flight 739 arrived at Wake Island at 03:54 on the 15th of March. Again, minor maintenance was required. The aircraft was serviced, the four cabin crew were replaced, and the flight departed for Guam at 05:15. This leg was six hours and the flight arrived in Guam at 11:14.

At Guam, the aircraft was serviced and refuelled. No maintenance was required. The next leg, to Clark Air Force Base in the Philippines, was estimated at six hours and nineteen minutes. The aircraft held enough fuel for nine hours and thirty minutes of flight.

The aircraft departed Guam at 12:57. Guam Air Route Traffic Control Centre established radar contact soon after take-off. The flight crew then contacted Guam International Flight Service Station to request that their departure message was relayed to the Flying Tiger Line offices.

At 13:25, the flight crew contacted Guam International Flight Service Station again to request a change in cruising altitude from 10,000 feet to 18,000 feet. No reason was given for the request and the flight crew were advised to contact Guam Centre. Guam Centre approved the request.

At 13:28 the flight crew reported climbing through 11,000 feet. Guam Centre advised the flight that it was 100 miles west of Guam and that radar services were being terminated.

At 13:33 the flight crew reported to Guam International Flight Service Station that they were 100 miles out and cruising at 18,000 feet.

The last transmission from the aircraft took place at 14:22. The flight crew contacted Guam International Flight Service Station and reported cruising over the clouds (“on top”) at 18,000 feet, along with their position from 14:16 and their current estimated position. They expected to arrive at Clark Air Force Base at 19:16 and said that they had 8 hours and 12 minutes of fuel remaining. All of the radio calls were completely routine: there was no indication of any problem or difficulties.

A little over an hour later, Guam International Flight Service Station suffered heavy radio static while speaking to another flight en route to Okinawa. At 15:39, the operator attempted to contact flight 739 in order to receive the now-overdue 15:30 position report. He was unable to establish radio contact.

At 16:00, Guam Centre declared the flight to be in an uncertainty phase (INCERFA) in line with Oceanic Emergency Procedures. This means that there is concern about the safety of an aircraft or its occupants.

At 16:33, after attempts to contact the aircraft had failed for over an hour, the status was upgraded to alert phase (ALERFA). This means that there is apprehension about the safety of an aircraft and its occupants.

The distress phase (DETRESFA) was initiated at 19:33 after continuous attempts to contact the aircraft by all stations and aircraft in the area had failed.

The distress phase means that there is reasonable certainty that the aircraft and its occupants are threatened by grave and imminent danger, including lack of contact and the risk of fuel exhaustion. Search and Rescue operations were initiated from Guam and the Philippines.

At 22:27, by which the time the aircraft would have exhausted all of its fuel, Tiger Flying Lines flight 739 and all of its occupants were declared lost.

The fate of the aircraft was unknown but then a call came in from a super tanker at 21:05, while the search and rescue operations were in progress. The shipboard lookouts had seen a mid-air explosion at 15:30 (1:30am local time).

The crew said that the night was moonlit and clear, with a quarter of the sky covered by small cumulus clouds, evenly distributed.

They first noticed a vapour trail or something similar overhead and slightly to the north of the tanker, moving in an east-to-west direction. At the time, the tanker was cruising on a heading of 077 degrees. The vapour trail passed behind a cloud and then there was an “intensely luminous” explosion consisting of a white nucleus surrounded by a reddish-orange periphery with radial lines of reddish-orange light. The explosion consisted of two pulses, lasting two to three seconds. The crew believed they saw two flaming objects of unequal brightness and size fall, at disparate speeds, into the sea. As they fell, a crew member noticed a small bright target on the ship’s radar, bearing 270 degrees at a range of 17 miles.

The captain arrived on deck to see the fall of the slower object before it disappeared into the sea. He estimated its position in reference to a star and ordered the ship’s course reversed. They aligned the heading of the vessel with the star and the captain found that the tanker’s heading was now 270 degrees, the same as the bearing of the target seen on radar.

The tanker continued to the position of the radar target but found nothing there. They searched the area for 5½ hours but found no trace of wreckage or debris. The crew were unable to establish contact with the US Navy radio stations at Manila and Guam and eventually decided that the explosion must have been some kind of military or naval exercise. The tanker broke off the search and resumed her course.

The approximate location of the mid-air explosion was confirmed to coincide with the estimated position of the aircraft at that time.

The subsequent search was cited at the time as one of the most extensive ever conducted.

No trace of the aircraft or the occupants was ever found.

No explanation was ever found either. Investigators found that although the aircraft was properly certificated and was in airworthy condition, a few weeks earlier, it had exhibited significant power loss to one of its engines after 3½ hours of flight which had not been explained but after minor maintenance, it appeared to be in good repair. There was no sign that day that there were any mechanical issues with the flight.

As a result, many believed that the aircraft may have been sabotaged.

The investigation found that the flight line and ramp areas at Honolulu, Wake Island and Guam were not secure and anyone could enter and access non-military aircraft parked at the airfields. Specifically at Guam, the last stop, the aircraft was left unattended in a dimly lit area for some time.

The explosion, as witnessed by the tanker, happened at the point when flight 739 should have been radioing in for the next position report. This seems extremely coincidental and is one of the reasons why many believe that the aircraft may have been sabotaged.

In addition, a second Flying Tiger Line flight was destroyed. An identical Lockheed Super Constellation, said to have been carrying secret military cargo, also departed Travis Air Force Base on the same day and encountered difficulties several hours later. The pilot appeared to encounter issues on the instrument approach and crashed short of the runway. The main landing gear was torn off and then the aircraft caught fire; six crew members received minor injuries and one was trapped in the cockpit and died in the fire.

Flying Tiger Line stated at the time that sabotage of one or both planes or a kidnapping of flight 739 were possibilities but they had no evidence to back up these theories. The executive vice president told the media that is was impossible for an explosion to occur on the Super Constellation in the course of normal operation: something violent must have happened.

The Civil Aeronautics Board believes that the crew members of the tanker most likely witnessed the explosion of the aircraft. However, they concluded, as no portion of the aircraft was ever recovered, it was impossible to determine whether mechanical/structural failure or sabotage caused the loss of the aircraft.

The original accident report has been scanned and put online as a PDF.

Whatever happened must have happened quickly, as the crew never had a chance to alert anyone that there was an emergency. As no one has ever taken responsibility for sabotaging the aircraft and the wreckage is unlikely to be recovered, this is a mystery that may remain forever unsolved.