They have two Curtiss C-46 from 1945. Its interesting that its cheaper to continue to pay for the maintenance and fuel than lease something more modern.
Replacements don’t exist. Those old prop liners can operate off unimproved dirt strips, grass, even snow and ice - and off short runways too.
Jets don’t like that.
For back country missions the only thing maybe better than a DC-3 is a Basler... and that is a modernized DC-3 with reinforcements and turboprops for more power. They suck a lot more fuel than a plain DC3 though, which can be problematic as some of these fields they have to fly fuel in.