Dave:
I was an Air Force photographer for 22 years. Part of that time was spent in Air Force mapping and spy plane units (U2 and SR71). Unfortunately, the Air Force thought of aerial photography as intelligence and not as history. The film was burned to extract the silver from it. Photography was recycling a long time before anyone else ever heard of it. The silver in the film was viewed as more valuable than anything in the photos...a real shame. To think that there were aerial photos of the entire D&RGW/RGS made before and during WWII and that it is apparently all gone.