The Air Force grounded its fleet of F-35 fighter jets Thursday as a safety precaution after a fire on one of the planes forced an aborted takeoff this week.The suspension applies to the Air Force’s 45 “A model” planes. The Defense Department didn’t direct a halt to testing of the Marine and Navy versions of the jet, known as the joint strike fighter.The grounding marks the latest setback for the F-35, which is built by Lockheed Martin Aeronautics in Fort Worth. The order was issued after an emergency at Eglin Air Force Base in Florida on Monday, when a fire in the rear of one plane forced the pilot to abort a takeoff. Emergency responders used foam to extinguish the blaze, and the pilot was not hurt.“As a precautionary measure, the Air Force has decided to temporarily suspend all F-35A operations until it is determined that flights can resume safely,” the Air Force said in a statement. “This is not an uncommon practice following a mishap. It ensures the safety of our crews and our aircraft so we can determine there is no fleet-wide issue that needs to be addressed.”The cause of the incident remains under investigation, Army Col. Steve Warren, a Pentagon spokesman, told reporters. The Marine Corps hasn’t flown its 31 F-35s for two days and is assessing daily whether to suspend operations, said Capt. Richard Ulsh, a Marine spokesman. The Navy is still assessing whether to issue a servicewide suspension, but some of its planes have been grounded, said Lt. Jackie Pau, a Navy spokeswoman. The Air Force halted F-35 flights immediately after the fire, but an Eglin spokesman said Tuesday that flights would resume Wednesday. That didn’t happen. The Air Force’s F-35s are at four bases: Eglin, Luke Air Force Base in Arizona, Nellis Air Force Base in Nevada and Edwards Air Force Base in California, said Maj. Natasha Waggoner, an Air Force spokeswoman. Lockheed will assist in the fire investigation, said Gordon Johndroe, a spokesman for the Bethesda, Md.-based company. He referred further questions to the Air Force. Two weeks ago, the Pentagon ordered that all F-35 engines be inspected after an “in-flight emergency” on June 10, when a Marine Corps F-35 had to return to base at Air Station Yuma in Arizona after its engine lost oil. No one was injured. Inspections of three other planes at the station revealed “suspect findings,” the Defense Department said in a statement. Last year, the Pentagon grounded all F-35s after a routine engine inspection revealed a crack on a turbine blade in a test aircraft at Edwards Air Force Base. Flights resumed about a week later after further inspections found no other problems. Lockheed and Pentagon officials have cited progress in the past year on technical issues that have dogged development of the F-35 and driven up its cost. But Frank Kendall, the Pentagon’s top weapons buyer, has said it hasn’t demonstrated enough reliability improvements. There’s “some marginal evidence of improvement, but it’s not enough,” Kendall told reporters June 12. Lockheed officials in Fort Worth have said they hope to boost production of the aircraft from about 36 this year to more than 120 a year by the end of the decade. Higher production would reduce the average cost of the plane, which now tops $100 million.Lockheed has been planning to take the jet overseas next month to fly for the first time at the Farnborough International Airshow.Lockheed employs more than 13,000 in west Fort Worth. The company’s top executive in Fort Worth said last week that increased production could add more than 1,000 jobs. This report includes material from the Star-Telegram archives.