The Pentagon suspended flights of the F-35B, the Marine Corps model of the joint strike fighter, after a propulsion-system part failed and caused a pilot to abort a takeoff."We are assessing potential causes and evaluating actions to return" to flight, Pentagon spokesman Joe DellaVedova said Friday.The Marine Corps model, designed for short takeoffs and landings on carriers and amphibious-warfare vessels, is the most complex of three models being built by Lockheed Martin in Fort Worth.The failure was in the propulsion system, made by Pratt & Whitney.It occurred before takeoff Jan. 16 at Eglin Air Force Base in Florida."The pilot aborted takeoff without incident and cleared the active runway," DellaVedova said.Development of the F-35 has been marked by delays and cost increases. The Pentagon's $395.7 billion estimate for developing and producing 2,443 fighters is 70 percent more than when the initial contract was signed in 2001.The incident involved a propulsion fueldraulic line, which saves weight by using jet fuel instead of the customary hydraulic fluid to lubricate mechanical parts."An initial inspection discovered a detached fueldraulic line in the aft portion of the engine compartment," said Matthew Bates, a spokesman for Pratt & Whitney, said in a statement.DellaVedova said, "it is the first time we've experienced an event with the propulsion fueldraulic line."The affected component isn't used on the Navy or Air Force versions, he said.