On August 2nd 1947, a British civilian version of the wartime Lancaster bomber took off from Buenos Aires airport on a scheduled flight to Santiago. There were 5 crew and 6 passengers on board the plane - named "Stardust". But Stardust never made it to Santiago. Instead it vanished when it was apparently just a few minutes from touchdown. One final strange morse code radio message - "STENDEC" - was sent, but after that nothing more was heard from the plane.

Despite a massive search of the Andes mountains no trace of the plane was ever found. For 53 years the families of those who disappeared have not known what happened to their loved ones.

But earlier this year the plane suddenly reappeared on a glacier high up in the Andes, more than 50 km’s from the area where the plane was last reported. In February this year the Argentine army arranged a major expedition to visit the crash site beneath the massive Tupangato peak (6800m). Their aim was to bring back the human remains which had been found at the site, so that an attempt could be made at identifying them. The expedition also offered a unique opportunity for crash investigators to see if they could finally explain what happened to the ill-fated plane.

'Horizon' gained exclusive access to this expedition, and now for the first time the full story of what happened to "Stardust" can be told. Why did the plane crash without warning? Why was it so far from its planned route across the mountains? What was the meaning of the last mysterious message - "STENDEC" - sent by the plane’s radio operator? Would it be possible more than 50 years after the crash to identify the remaining fragments of human remains that so graphically testified to the horrific destructive forces involved in the crash? And perhaps most mysteriously, why did the wreckage elude discovery for so long, despite regular mountaineering trips to Tupangato over the years?

The expedition was joined at an army base in the Andes foothills. The threat of altitude sickness and the approach of winter meant that the trip required meticulous planning. More than 100 mules were used on the four day journey to the crash site, ferrying people and supplies to base camp, and then on up to an advance camp on the glacier. Several mules fell on the perilous journey over a 4500m pass; others bolted.

After four gruelling days the expedition finally reached the Tupangato glacier. They had enough supplies for 36 hours to investigate the crash site and finally explain what had happened to Stardust, and why it had disappeared for so long. At the crash site 'Horizon' followed the crash investigator as his ideas on the crash changed with each new discovery. The plane’s main wheels were discovered, one still fully blown up. One of Stardust’s Rolls Royce engines was lying on the ice, and nearby it’s propeller. Damage to the propeller indicated that the engine was working normally at the time of the crash. The wreckage offered no smoking gun to explain why the crash happened.

Human remains were discovered - a hand, parts of a torso half buried in ice, fragments of hair - poignant reminders that this was above all a human tragedy. At a lab in Buenos Aires scientists are still trying to extract sufficient DNA from the remains to allow the remains to be identified. Few of those who went down with the aircraft were old enough to have children, so DNA matches are being made with more distant relatives, further complicating the work. The difficult task of identifying the remains brought down from Tupangato is still underway.

Meanwhile the air crash investigators focused on the mystery of why the plane had not been found for so many years. Their analysis led them to suspect that the reason the plane had remained hidden for so long could lie with the glacier the wreckage was lying on. As soon as they returned from the mountains the investigators visited a glacial specialist in Mendoza. He told them that if the plane had crashed on the upper part of the glacier it would have been gradually buried by year on year snowfall, until it became a part of the glacier itself. It would then have travelled downhill with the glacier under the influence of gravity. Eventually it reached a warmer zone, and here the ice started to melt. Gradually, out of the melting ice, came the remains of Stardust. The wreckage hadn’t been found because for more than 50 years it had been buried inside the glacier.

Stardust isn’t the only plane to be buried inside a glacier. In Greenland an entire squadron of second world war aircraft which crash landed on top of the Greenland ice cap in 1942 were recently discovered a hundred metres under the ice. They too had been buried by years of snowfall which gradually hardened into ice, until planes and glacier became one.

But having solved the mystery of why Stardust had disappeared for so long, much hard work remained - particularly trying to explain why the plane was more than 50 miles off course when it crashed. The Argentine investigation needed to explain why a highly experienced crew could make such a massive error. They focused on a meteorological phenomenon that was virtually unknown in 1947 - the 'jetstream'. This high altitude wind can blow at more than one hundred miles an hour. But in 1947 very few planes flew high enough to encounter the jetstream. Stardust was one of the exceptions.

On the day of the flight bad weather over the Andes persuaded the crew to fly close to the plane’s maximum altitude, so they could fly over the top of the weather… and the mountains. Stardust’s superior performance should have guaranteed it’s safety. But in fact it was the decision to fly high that was at the root of the disaster. Unknown to the crew, they were flying straight into the jetstream. And because of the bad weather, they couldn’t see the ground, so they had no way of knowing that the jetstream was dramatically slowing them down. It meant that although the crew’s calculations showed they had crossed the Andes, in fact the jetstream’s powerful wind meant they were still on the wrong side of the mountains. So when Stardust began it’s descent, rather than being above Santiago airport, it was on a collision course with Mount Tupangato.

The jetstream finally explained the reason for the massive navigation error, and therefore the crash. But the investigators were unable to explain one final mystery, the last radio message - Stendec - sent by Stardust just before the crash. Many explanations have been advanced, but to this day none has convincingly explained what the message meant.

'STENDEC' - Stardust’s Final Mysterious Message

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