As many as six firefighting aircraft have been grounded at a time due to a shortage of pilots, the Sacramento Bee said. Nearly 20 percent of the fleet of the Grumman S-2T low-flying tanker aircraft was grounded during the month of August. Within the past year, Cal Fire has lost 10 air tanker pilots to retirements, medical absences, other job opportunities and one death. Cal Fire’s chief of flight operations, Dennis Brown, said there are eight pilots currently in training and he estimates the need to hire about 40 pilots in the next few years. Another problem, Brown said, is that less than half of the trainees historically decide to actually work as air tanker pilots.