Following the deadly crash of an an S-2T tanker near Yosemite, Cal Fire has grounded all 23 planes of that type in its fleet for inspection.
S-2T planes were built by the U.S. Navy between the 1950s and 70s for anti-submarine warfare.
"They were converted in the 70s for firefighting," Cal Fire spokesperson Daniel Berlant said. "They went through extensive reconfiguration, modernization, to be able to fight fire."
In a Tuesday evening conversation with FOX40, Berlant described the planes as "the heart of our fleet" and said they are maintained rigorously. They hold approximately 1,200 gallons of retardant, and are the initial air response to wildland fires.
"We have spent a lot of time and a lot of energy ensuring that our aircraft are maintained and are mission-ready, especially in a year like this when we have so many fires," Berlant said. "We're going to be working with the NTSB and with the FAA as they investigate exactly what happened in this accident."
The U.S. Forest Service has tankers that will continue to be used during the grounding of Cal Fire's S-2T tankers.