Air Force and Marine Corps F-35 pilot training was initially slated to begin about a year ago, but was delayed by the Pentagon after its chief tester, Michael Gilmore, raised concerns about the maturity of the new plane and its software.

Gilmore, the Pentagon’s director of operational test and evaluation, declined to comment on Wednesday on the Marine Corps’ decision to skip the operational utility evaluation, according to his spokeswoman.

Lockheed is developing the multirole stealth F-35 for the U.S. military and eight international partners at a projected cost of around $396 billion.

Britain’s BAE Systems is a key contractor on the project. Other subcontractors include Northrop Grumman Corp and United Technologies Corp.

The Marines are likely to be the first of the U.S. military services to declare them ready for “initial operational capability” because they do not plan to wait for more sophisticated software upgrades required by the other services.

The Navy’s F-35C or carrier variant of the new fighter jet also recently completed testing of a redesigned arresting hook at a facility in Lakehurst, New Jersey.

One source familiar with the tests said they had proven largely successful, although there was still more work needed to ensure the jet could safely land on an aircraft carrier.