An "improperly crimped" fluid line was the probable cause of a propulsion-system leak that led the Pentagon to suspend flight tests of the F-35 fighter's Marine Corps version, according to the Pentagon.The investigation "ruled out any design or maintenance issues," Pentagon spokesman Joe DellaVedova said Monday in an e-mailed statement. The evidence revealed "a quality discrepancy" resulting in the crimped line, he said. Test flights of the Marine version, the F-35B, were stopped after a pilot aborted a takeoff because of a flaw in the propulsion system made by the Pratt & Whitney unit of United Technologies. The Jan. 18 flight suspension remains in effect, according to DellaVedova.Development of the F-35, which is being produced by Lockheed Martin in west Fort Worth, has been marked by delays and cost increases. The Pentagon's $395.7 billion estimate for the total cost of development and production of 2,443 fighters has increased 70 percent since the initial contract was signed in 2001.The Marine Corps' F-35B is designed for short takeoffs and landings.An audit of quality-control records has identified six additional "noncompliant units" that have been removed from aircraft and returned to Pratt & Whitney for replacement, DellaVedova said. The flawed part is only on the Marine Corps version."We have begun the process of removing the suspect" parts, and "we are performing additional X-ray imaging inspections," said Matthew Bates, a spokeswoman for Pratt & Whitney."The team continues to work diligently toward completing the investigation and implementing corrective actions with the supplier," Bates said. "We anticipate a return to flight" soon.