While it may seem impossible for a plane to just disappear, the fate of the troops aboard Flight 739 remains an enigma.

Image: Facebook/Remembering Flying Tiger Line Flight 739

On March 15, 1962, Guam International Flight Service Station attempted to make radio contact with an outbound plane that had left several hours prior. Alarmingly, though, the operator received no response in question. But what could have happened to the craft that was carrying troops to Vietnam? Well, some began to suspect that sabotage was at play.

Yes, the fateful plane from the Flying Tiger Line had been chartered by the U.S. military to transport Army Rangers and Vietnamese soldiers to Saigon. The flight was scheduled to be a long one, although there would be several stops to refuel. And, sadly, it was during the leg between Guam and the Philippines that contact with the aircraft was lost.

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Then, when it was found that the plane had disappeared, the disturbing news prompted what was at that point the largest search and rescue operation in history. And, naturally, many theories have since emerged about what ultimately happened to Flying Tiger Line Flight 739 and its passengers and crew. But could someone have really deliberately tampered with the craft?

In any case, it’s certainly not unknown for airplanes to seemingly disappear into thin air. Amelia Earhart was the first woman pilot to traverse the skies over the Atlantic and became one of the most famous flyers in history. Yet she vanished without a trace on an attempted round-the-world flight in 1937. And even more than 80 years on, it’s still not determined what brought her plane down.

More recently, in 2014 Malaysia Airlines Flight 370 made headlines around the world when it vanished while flying between Kuala Lumpur and Beijing. And the scale of the hunt for the missing plane reminded some of the long-ago search for Flying Tiger Line Flight 739.

The Flying Tiger Line itself was the first airline in the U.S. to run scheduled flights for cargo, using planes bought from the U.S. Navy. And while the pilots and ground crew of the fledgling service couldn’t afford to launch such an endeavor on their own, oil magnate Samuel B. Mosher fortunately stepped in to match their investment and get the Flying Tiger Line off the ground.

The airline took its name, moreover, from a unit of fighter jets in the Second World War. Flying Tiger pilots were a mixture of Army, Navy and Marine Corps personnel who rapidly became famous for the shark-face motifs that adorned the noses of their aircraft. When ten pilots from the outfit set up the cargo business after the war, then, the moniker came with them.

Yet although Flying Tiger Line’s main business at first was flying cargo domestically across America, it also made some longer journeys. U.S. troops were still occupying Japan, after all, meaning the firm began to fly trans-Pacific routes to deliver supplies to the men. And the plane used on the fateful trip in March 1962 was a Lockheed L-1049H Super Constellation.

Flying Tiger Line had owned the four-engine plane since 1957, and the 113-foot-long craft with a wingspan of 123 feet had flown over 17,000 hours with no previous problems. When empty, the Super Constellation weighed about 73,000 pounds, but it could bear almost its own weight again in cargo. And on the day the plane vanished, it was carrying 25,552 pounds of gasoline.

During a normal flight, the plane would travel at about 260 knots – roughly 300 mph. It could go quicker if it was flying under 11,000 feet in altitude, and it could reach a maximum height of 25,000 feet. The longest non-stop journey it was able to make was 4,140 miles.

And in 1962 Flying Tiger Line had been running for nearly 20 years. On March 14, then, business may have been as usual at first when one of the airline’s planes took off from Travis Air Force Base in California. The routine long-haul flight, which was bound for Saigon in Vietnam, would require several fuel stops en route – namely at Honolulu, Wake Island, Guam and the Philippines.

On the day in question, 96 people were traveling on the Super Constellation alongside the two flight crews and four members of the cabin crew. The group included the captain, the first officer and the second officer as well as two navigators and a pair of engineers.

And the 48-year-old captain, Gregory P. Thomas, had a reputation as a “colorful and heroic flyer.” Of his impressive 19,500 hours in the air, 3,562 of these had been in Lockheed L-1049H crafts. Thomas had worked for the Flying Tiger Line since 1950, too, and had his airline transport pilot certificate. Overall, then, he was well-qualified and more than capable of the task at hand.

Thomas’ first officer, Robert J. Wish, was also aged 48 and was based in California. And while Wish had clocked up slightly fewer flight hours – 17,500 – than the captain, he had nevertheless gained plenty of experience by working for Flying Tiger Line from 1951.

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Meanwhile, the second officer was 39-year-old Robbie J. Gayzaway – sometimes spelled Gazaway or Gazzaway. Another Californian, he’d been working for Flying Tiger since 1953. Of his 5,000 flight hours, though, only 900 were in the Super Constellation. And although Gayzaway had his ATP certificate, he was not qualified on as many types of aircraft as his senior colleagues.

Both flight engineers also hailed from California. George Nau, aged 38, had started working for Flying Tiger in 1956. He had an FAA flight engineer certificate and 1,235 hours of experience in the L-1049H. His fellow engineer, Clayton E. McClellan, also had upwards of 1,000 hours’ worth of flight time in such an aircraft.

And William T. Kennedy and Grady Burt, Jr. were both navigators, with the pair also possessing radio operator licenses. Kennedy was 45 and had begun working for Flying Tiger Line in 1962, while Burt had been hired a year later,. The crew was completed by senior flight attendant Barbara Walmsley and her fellow cabin staff: Patricia Wassum, Hildegard Muller and Christel Reiter.

Image: Trish Harris, USASOC Public Affairs Office

As previously mentioned, though, the plane’s passengers weren’t just ordinary civilians. The aircraft had been chartered by the Military Air Transport Service, you see, and 93 of those on board were Army Rangers. These men had been specially trained in the jungle, with most being experts in communications and electronics. In addition, there were three Vietnamese service personnel on the trip.

And the ill-fated flight left Travis Air Force Base at 5:45 a.m. GMT on March 14. At first, though, everything went like clockwork, and the plane reached Honolulu as planned at 5:44 p.m. GMT. There was a slight hold-up while on-board rest facilities were checked after concerns had been raised by the crew, but at 8:40 p.m. GMT they were in the sky again. There were absolutely no concerns over the Super Constellation’s fitness to fly, either.

So, with the flight still proceeding as expected, the plane continued to Wake Island. After landing at 3:54 a.m. GMT on March 15, a new cabin crew then replaced the original four, and the aircraft was serviced. Again, only minor maintenance was carried out. And when the plane reached Guam at 11:14 a.m. GMT, it needed nothing more than servicing and refuelling before continuing on its journey.

The next stop on the journey was meant to be the Philippines. The plane would be in the air for six hours and 19 minutes for this leg – and as it had fuel for over nine hours of flying, that shouldn’t have been a problem. And when traffic controllers established radar contact with Flight 739 soon after take-off, all seemed to be going well.

Image: US Air Force. Tech. Sgt. Mike Andriacco

Nevertheless, there was one strange moment at 1:25 p.m. GMT. At that time, the crew radioed back to Guam to say that they wanted to raise the height at which the plane was flying, but no reason was given; after that, the team got permission to climb from 10,000 feet to 18,000 feet. Then, a few minutes later, the plane was out of range of Guam’s radar and continuing on its journey. And at 1:33 p.m., the crew radioed the Super Constellation’s position as 100 miles distant.

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What’s more, everything still appeared in order when another transmission was received at 2:22 p.m. GMT. On that occasion, the crew told Guam that they were still flying at 18,000 feet and above the cloud cover. They also stated their current position and gave an estimate for the time they would arrive at Clark Air Force Base: 7:16 p.m. However, this would be the last contact that anyone would have with the plane.

Image: Topical Press Agency/Getty Images

Then, later that day, Guam International Flight Service Station started having trouble with its radio transmissions. As the station attempted to communicate with a plane that was on its way to Okinawa in Japan, for example, there was heavy static over the airwaves. And when the operator tried to contact Flight 739 for an overdue status report, it alarmingly received no response at all.

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At 4:00 p.m. GMT on March 16, 1962, then, the first stage of emergency procedures was instigated when INCERFA – or a state of uncertainty – was declared. This meant that worries about the plane and the people on board were official, but they were not yet serious. When further attempts were made to contact Flight 739, though, these also ultimately proved unsuccessful.

So, the INCERFA status was upgraded to ALERFA – or an alert phase – at 4:33 p.m., rising to DETRESFA three hours later. This distress phase meant that the missing plane and its passengers and crew were in immediate and severe danger. And as a result, search teams were duly launched from both Guam and the Philippines.

Yet while the initial exploration was fruitless, the authorities were nevertheless contacted by a supertanker at 9:05 p.m. Apparently, the crew on board the ship had spotted something strange at 3:30 p.m. GMT, or 1:30 a.m. local time. The sky had been mostly clear and the moon bright then when a vapor trail had appeared in the sky. This phenomenon was then followed by what has been called an “intensely luminous” explosion behind the clouds.

Image: Facebook/Remembering Flying Tiger Line Flight 739

According to the ship’s crew, the explosion had come in two flashes that had each only lasted a couple of seconds. A reddish-orange rim had surrounded a bright white center, while further trails of a reddish-orange color had expanded outwards. And as the crew watched, two differently sized objects appeared to fall burning into the sea.

Looking at the ship’s radar, one of the crew members saw it marking a target 17 miles away. Then, when the captain reached the bridge in time to see the second object fall, he made note of where it was relative to a star. The men had the information they needed, then, to head towards the source of the explosion.

Image: The Allen Collection via This Day in Aviation

When the supertanker reached the supposed site of origin, however, there was nothing but empty sea. And although the crew on board the craft subsequently spent more than five hours searching the area, they didn’t even find debris. With no radio contact with either Guam or Manila, the men therefore decided to write the whole thing off as some kind of military exercise – and they moved on with their scheduled journey.

Later, it was calculated that the explosion would have been roughly where Flight 739 had been, although that didn’t help in finding the remnants of the plane. The Super Constellation was thus officially declared lost at 10:27 p.m. GMT – the point at which it would have had no fuel left. And there was still no shred of evidence of either the aircraft or its crew.

During the search, 1,300 people, eight surface vessels and 48 aircraft jointly covered 144,000 square miles of territory, while rescue team members spent 3,417 hours in the air flying 377 separate sorties. In its day, it represented the most extensive search ever conducted in aviation history.

There was no conclusive evidence about what had happened to the Super Constellation, either. The only quirk in its history had been a brief power loss a few weeks previously on a flight, but the single engine affected had soon been fixed. Indeed, there had seemingly been no problems on the day of the plane’s final journey, and the craft itself had been certified safe.

So, with mechanical failure seeming an unlikely cause, a new theory became popular. Many people began to believe that the plane must have been sabotaged, and the idea was not implausible, either. After all, Flight 739 had stopped at Honolulu, Wake Island and Guam – all of which had low runway security. It would have been relatively easy, then, for an outsider to access the plane.

And if someone had sneaked aboard in order to sabotage the plane, it was most likely to have been at Guam. You see, not only did the airfield reportedly lack decent security, but it was also said that the plane had been left unattended at the location. Lighting around the aircraft was described as poor, too. So, taking all of this into account, foul play seemed a credible explanation.

According to an executive vice president of Flying Tiger Line at the time, the only certainty was that something violent must have caused any explosion on the Super Constellation. Additionally, it was probable that whatever occurred had happened quickly – otherwise the crew could have radioed for help.

Flight 739 was not the only Flying Tiger Line plane to be lost in mid-March, either – lending credence, perhaps, to the claims of potential sabotage. And, eerily, the second plane was also a Super Constellation, and it too had taken off from Travis Air Force Base on March 14. Furthermore, it’s been reported that the nature of the craft’s cargo was kept secret by the military.

Captain Morgan W. Hughes was piloting the fateful plane on flight N6911C from Travis Air Base to Kadena Air Force Base in Okinawa, Japan. And while the Super Constellation was due to land on Adak Island off Alaska, something went tragically wrong. The craft’s runway approach was too low, while seven separate warnings given by air traffic controllers were apparently all ignored.

And the plane was just over 300 feet short of the runway when its wheels struck rocks. It then skidded along the runway for 2,000 feet, catching fire as it slowed to a halt. Flight engineer James M. Johnson was killed and six other crew members were injured in the crash, which was later blamed on “misjudgement of distance and altitude.”

To this day, however, the fate of Flight 739 is still considered a mystery. And although the Civil Aeronautics Board has concluded that the explosion seen by the supertanker was probably caused by the plane, that doesn’t explain how or why it happened. So, with no wreckage to examine to prove theories of failure or sabotage, the episode seems destined to remain an enigma.