Most Australians today have never heard of Southern Cloud. Yet thousands fly over its wreck site every day, blissfully unaware that this aircraft played a part in the safe air travel that we enjoy.

The loss was Australia's first major civil aviation disaster.

Southern Cloud was one of five aeroplanes operated by Australian National Airways (ANA), launched by Charles Kingsford Smith and Charles Ulm in 1929 during the pioneering days of Australian aviation. Kingsford Smith and Ulm were national heroes, having earlier flown across the Pacific in the Southern Cross in a blaze of publicity.

Southern Cloud took off from Sydney's Mascot aerodrome on the morning of March 21, 1931, bound for Melbourne. A few hours later the weather bureau changed its forecast from "windy and rainy weather" to a warning of virtually cyclonic conditions over the Australian Alps. But there was no way to communicate the news to Southern Cloud - the plane had no radio.

Piloted by experienced World War I flyer Travis Shortridge, with Charlie Dunnell as co-pilot, Southern Cloud carried six passengers: businessman Hubert Farrall, theatre producer Clyde Hood, engineer Julian Margules, accountant Bill O'Reilly, and Claire Stokes and Elsie Glasgow who were on holiday. It was Claire's first plane trip.

The aircraft failed to arrive at Essendon. Co-ordinated by the Civil Aviation Branch of the Department of Defence, a major search effort began. It included Kingsford Smith, Ulm, other ANA pilots, RAAF personnel, private flyers, and ground parties. But despite huge numbers of so-called ''sightings'', no sign of the missing plane could be found. The story pushed Great Depression headlines off newspaper front pages. ANA went bankrupt soon after.

The official inquiry which followed could only conclude that the weather conditions on March 21 had played a major role in the plane's disappearance. One of the inquiry's major recommendations was that radios and qualified operators be made compulsory in regular passenger services, so that updated weather information could be communicated to aircrew aloft.

Southern Cloud helped create safer air travel for all Australians.

By October 1958 the Snowy Scheme was in full swing in the extremely wild Tooma River valley west of Cabramurra. One worker, Tom Sonter, was bushwalking during his day off. Unable to reach his target Black Jack Mountain he turned back, and stumbled upon wreckage. Within days, DCA officials and police confirmed the wreck was Southern Cloud.

As well as journalists, souvenir hunters descended on the site and much of the plane's remains were removed. Some ended up in Cooma's main street memorial erected in 1962. Others were kept in private hands and a few have since been donated to museums, including the National Museum of Australia in Canberra.

The crash site is in one of the most precipitous parts of the Great Dividing Range. It is a place visited by few. It is a place torn by gales and blizzards in winter, and burned almost to destruction by bushfire in summer. It is a place of towering alpine ash eucalypts, and ragged rockfaces and tumbling streams. It is a place that deserves to be remembered. I have gone to it time and again during the last 35 years.

In 1984 I was researching an article on Southern Cloud which was subsequently published in the Canberra Historical Journal and Australian Aviation. As part of this research I organised for a group of us to walk to the crash site in December. A Snowy Scheme gravel road (walkers only) runs nearly to the site, and from there you follow a foot-track for a few hundred metres. It is steep, overgrown and log-strewn. I was moved to find a memorial amid the remaining wreckage and surrounding eucalypts on the wild mountainside.

Since then I have taken numbers of friends to the site, and in 2008 as a senior curator at the National Museum I was involved in the 50th anniversary celebrations organised by the Tumbarumba Museum. A highlight of the event was the presence of Tom Sonter.

I found Tom to be a quiet, gentle man, whose life had been strongly influenced by a love of the bush. A large number of us, aided by Snowy Hydro vehicles to at least get to the end of the Snowy road, were able then to walk the final distance to the site. For Tom it was a moving experience to return to this place where he had five decades earlier solved - completely by accident - a great aircraft mystery.

I've been back several times since. Clinging on to that steep slope, with the Tooma way down below and Jagumba Mountain sticking up across the deep valley, the eucalypt forest enclosing all, I've been glad to be back and to pay respect once more to those people on board. Eight people who thought they were flying to Melbourne, but flew into Australia's aviation history instead.