(Adds details, Lockheed statement)
By Andrea Shalal
WASHINGTON, June 23 (Reuters) - The U.S. Air Force on Monday temporarily halted flights at a Florida air base of 26 F-35A fighter jets built by Lockheed Martin Corp after a jet caught fire as it was preparing to take off for a training flight, a Pentagon spokesman said.
The pilot aborted the takeoff and was not injured, said Joe DellaVedova, spokesman for the Pentagon's F-35 program office. He had no immediate details on the cause of the fire or extent of the damage to the F-35 conventional takeoff model.
The fire occurred in the rear part of the plane where the engine is located, but it was unclear whether the engine was involved. Engine maker Pratt & Whitney, a unit of United Technologies Corp, said it was aware of the incident and stood ready to assist in the Air Force investigation.
The incident came just days before a group of F-35 B-model jets are due to fly to Britain for the jet's international debut. One U.S. defense official said it was too soon to say whether the fire would delay those plans or affect them in any way.
DellaVedova said it was unclear what caused the fire, but Air Force officials had temporarily suspended flights of the A-model jets at the base until the root cause was found.
"Safety is paramount, and all F-35A flight operations have been temporarily suspended at Eglin as they investigate the nature of the incident," he said.
Emergency responders were able to put out the fire, which occurred about 0915 local time, he said.
Lockheed referred questions to the 33rd Fighter Wing, which is responsible for training F-35 pilots for the Air Force, Navy, Marine Corps and international militaries.
This is the second incident that has affected F-35 flights in recent weeks. The U.S. military ordered mandatory inspections of all 97 F-35 fighter jets earlier this month after a Marine Corps F-35 B-model jet suffered an oil leak in flight.
The incident was resolved quickly, and all but three jets returned to flight status with days. Those three jets are being repaired to deal with a faulty part, the F-35 spokesman said.
It was not immediately clear whether the fire would trigger fleet-wide inspection orders for all three models of the F-35.
Lockheed is building three models of the new warplane for the U.S. military: a conventional takeoff version for the Air Force, a short takeoff and vertical landing version for the Marine Corps, and a carrier-based version for the Navy.
Britain helped fund development of the radar-evading jet, along with seven other countries: Australia, Norway, Italy, Denmark, the Netherlands, Turkey and Canada. Japan, Israel and South Korea have also placed orders for the warplane.
News of the fire also overshadowed a new report from the Pentagon's chief weapons buyer that showed the projected cost of retrofits required for the jet had dropped to $1.65 billion as of February 2014, from $1.75 billion a year earlier.
It said Lockheed was working closely with the F-35 program office to reduce the time required to implement design changes into the production line, which was helping to lower the cost. (Reporting by Andrea Shalal; Editing by Chris Reese and Ken Wills)