Cal Fire took delivery of 23 upgraded Grumman S-2 Tracker. Completely rebuilt by Marsh Aviation in Mesa, AZ, these aircraft kept the original Grumman airframes but were equppied with new wiring, internal parts and - most important - turbine engines. Due to the extend of the rebuild, they are now considered Marsh built, and not Grumman anymore. The last aircraft were delivered in 2005, with one (registered N449DF) suffering an accident on October 7, 2014, while combating a fire in the Yosemite National Park. N445DF used to be US Navy BuNo 152345.