The U.S. military cleared the F-35B short takeoff/vertical landing (Stovl) variant of the Joint Strike Fighter to resume flight operations last week, ending a grounding of more than three weeks that was ordered after a fuel line failed in a test aircraft at Eglin Air Force Base, Fla.

Military and industry engineering teams determined that an improperly crimped fueldraulic hose caused the failure. The hose uses fuel instead of traditional hydraulic fluid to drive the actuator movement for the F-35B’s vectoring exhaust system. Twenty-five development and production Stovl models were grounded on January 18. The F-35 Joint Program Office announced that F-35B flights were cleared to resume on February 12.

“All affected hoses have been inspected, and those out of tolerances will be replaced,” the JPO said in a brief statement. The aircraft “have been cleared for return to flight upon reinstallation of compliant hoses by airworthiness authorities at the Naval Air Systems Command and the F-35 program office.”