Inferno Entre Nuvens

I remember seeing this when I was a kid. A lot of the aviation shots were really great. "Wings" was before my time, and Howard Hughes spent a ton of money on it, but this one has great impact. It's real hard to find now. What is the best way to locate 1937 films now? Are a lot of them, being on nitrate film, now completely lost? Where can one find a listing of films of this nature, not GREAT films but good ones? Would there be a source which would have a lot of these on DVD now? Many WWI aviation films, such as "Dawn Patrol" etc. were made with aircraft of that era, since it was only 20 years or so since the end of that war. Try to find Nieuports, Spads, etc. now! It's important for historical as well as artistic reasons to locate these films.