The U. S. Forest Service has used DC-3 aircraft, since retiring the Ford tri-motor, for Smokejumping since the 1940's. Two "Dougs" are still in service (along with two other types of jump ships - Otters and Shepras), although they have been converted to turbine engines (and had the fuslage extended several feet) in the 1990's.
I was hauled to numerous wildfires out of McCall Idaho (before the upgrands). Always a treat, with the net seating, oil leaking and popping engines.
One memorable rough air flight from McCall to Helena had 19 of the 21 firefighters puking our guts out, while the pilot and co ate a hearly sack lunch....!
Picture of the McCall Jump ship:
Smokejumper Aircraft