The Pentagon and U.S. Navy have lifted flight restrictions on the Marine Corps version of the F-35 fighter jet, clearing the way for testing and training flights to resume after a nearly month-long grounding, military officials said on Wednesday.

The decision would allow officials to quickly resume flight tests of the F-35B, the Marines’ version of the new warplane being built by Lockheed Martin Corp, said Colonel Kevin Killea, who oversees aviation requirements for the Marine Corps.

He said, however, that the Navy and the F-35 program office had more work to do to resolve the manufacturing issues blamed for the grounding.

Resumption of test and training flights of the F-35B is good news for the $396 billion F-35 program, which must complete an aggressive schedule of test flights this year to keep the program on track after earlier delays.

The Pentagon and the Navy grounded all 25 F-35B jets on Jan. 18 after a fuel line made by Stratoflex, a unit of Parker Hannifin Corp, detached just before a training flight in Florida on Jan. 16. The Pentagon later said the issue stemmed from a manufacturing defect, not maintenance or design issues.

Joe DellaVedova, spokesman for the Pentagon’s F-35 program office, said all 25 F-35 B-model warplanes were cleared for flight as soon as any defective fuel lines had been replaced. He said all the affected hoses had been inspected and those found to have problems would be replaced. The hose in question is part of the exhaust system on the F-35B, which can take off from short runways and land like a helicopter.

Stratoflex is a subcontractor to Britain’s Rolls Royce Plc , but the prime contractor for the F-35B engine is Pratt & Whitney, a unit of United Technologies Corp.

The Pentagon’s F-35 program office lifted the flight restrictions on nine developmental test F-35B aircraft, and Vice Admiral David Dunaway, head of Naval Air Systems Command, followed suit later by approving flights by 16 additional F-35B jets that are being used for training, defense officials said.

Flights of the Air Force’s A-model and the Navy’s C-model of the F-35 were unaffected because they do not have the same fuel line involved in the incident that triggered the grounding.