DC-6s are still flying on a regular basis in Alaska with cargo airlines. They sound like nothing else in the air, and I heard one fly over a few nights ago. During the summer months, you can see a DC-6, DC-3 or C-46 fly by almost daily.C-54 Douglas Skymaster was another long life plane, with origins in WW2. I believe they flew in one form or another, until the 1990s.