If you live in a forest fire prone area, you've likely seen these big 4 engine turbo prop planes with red and white paint. They are P3 Orions converted to air tankers by the Aero Union corporation, the largest ariel firefighting contractor in the United States. They pioneered the development of airborne firefighting systems. Unfortunately, they're out of business. These tankers were arguably the best ariel firefighting planes ever converted from prior military use. They were fast in response times, had huge fuel capacity, and great slow speed characteristics.
http://wildfiretoday.com/2012/01/01/aero-union-to-auction-their-p-3-air-tankers/
http://wildfiretoday.com/2012/01/01/aero-union-to-auction-their-p-3-air-tankers/