Three separate leases with the U.S. Navy brought a total of 55 S-2s and 60 engines for the program. This allowed CAL FIRE to keep the fleet going until the mid-1990s when it was decided to upgrade from S-2A to S-2T air tankers. In 1987, CAL FIRE entered into an agreement with Marsh Aviation of Mesa, Arizona to build a prototype S-2T. This prototype was placed in service and used at several bases. The success of the prototype led to acquisition of 26 S-2E/G aircraft in 1996. The E/G series S-2 was larger and newer. It could haul 1200 gallons of retardant with two TPE-331 GR turboprop engines at speeds in excess of . A contract for building 23 of the new S-2T airtankers was entered into, with 13 delivered by the end of 2002, seven additional aircraft delivered and placed in service by the end of 2004 and the final three in 2005. As the new air tankers were delivered and placed in service, the original S-2As are retired.