Sometimes a purely symbolic achievement actually means something.

The Lockheed Martin F-35 programme has a lot of promises still to keep. Within five years, programme officials must now complete development of all three variants, reduce unit prices by 25% and sort out a current mess of a maintenance system.

Meeting those measures will be challenging enough on its own, but probably impossible given another downturn in public confidence caused by more missed deadlines and budget limits.

By declaring initial operational capability (IOC) with the first Lockheed Martin F-35B squadron on the last day of July, the US Marine Corps uses a mostly symbolic act to nudge the programme in the right direction.

In purely technical terms, passing the IOC milestone in July 2015, as promised in 2010, is not by itself significant. The USMC established its own criteria for achieving IOC, then came up with a waiver for one criterion that could not be met in time. Compared to the more rigid and consequential status of full operational capability, IOC is more symbol than substance.

But there is an unmistakable sense of momentum growing around the programme. The atmosphere seems completely changed from five years ago. At the beginning of 2010, the F-35 had just emerged from an infamous lost year, as the test fleet remained mostly grounded by technical glitches and the production system was a debacle. The head of the programme was sacked and Secretary of Defense Robert Gates acknowledged a new budget overrun and a three-year delay.

When the marines promised five years ago to achieve IOC of the F-35B in 2015, few would – or should – have believed them to keep their word.

But the programme really has changed. The back-to-back appointments of Vice Adm David Venlet and Lt Gen Christopher Bogdan transformed a dysfunctional F-35 joint programme office into a bureaucracy that actually solves problems.

The F-35, of course, will never satisfy a global chorus of critics who believe the fighter’s basic design is unworthy of its role regardless of how much time and money supports its development.

But the best argument against the F-35 has always been a decade-long track record of expensively broken cost and schedule commitments. The programme is by no means yet out of trouble, but the F-35B IOC milestone symbolises a recent period of progress and promises – finally – kept.