<a href="https://en.wikipedia.org/wiki/Douglas_C-1" class="extiw" title="w:Douglas C-1">Douglas C-1</a> Air Ambulance, forward interior view. (U.S. Air Force photo)
U.S. Air Force
National Museum of the U.S. Air Force, <a rel="nofollow" class="external text" href="http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=3237">Factsheets : Douglas C-1 Air Ambulance</a> (<a rel="nofollow" class="external text" href="http://www.nationalmuseum.af.mil/shared/media/photodb/photos/051127-F-1234P-002.jpg">image link</a>)