At the close of 2018, it seemed that 2019 might finally be the year Lockheed Martin’s flagship F-35 Joint Strike Fighter would start beating back the critics and proving the most expensive weapons platform in history was worth the cost and delays. With F-35s finally entering the fight with both the Israeli military and the U.S. Marines before the onset of 2019, the days of the most advanced fighter on the planet serving as little more than a technology demonstrator are finally behind us, but the F-35’s problems persist.

According to a report issued by the Office of Operational Testing and Evaluation, fewer than 60% of F-35s delivered to the United States are operational, meaning, there has been no readiness improvement over previous years despite new readiness efforts being mounted.

“There was no improving trend in fleet aircraft availability. Fleet-wide average availability is below program target value of 60 percent and well below planned 80 percent needed for efficient conduct of IOT&E,” the report says. “The trend in fleet availability has been flat over the past three years; the program’s reliability improvement initiatives are still not translating into improved availability.”

Although acknowledging that more than 40% of all delivered F-35s won’t fly anytime soon is bad, some could contend another glaring issue in the report is far more damning of the multi-role fighter that is expected to replace long-serving platforms as diverse as the F-16 Fighting Falcon and A-10 Thunderbolt: it’s close air support gun doesn’t seem to be very good.

Report: Air Force F-35's close air support gun doesn't work and only 60% of delivered jets fly
F-35A firing its single GAU-22/A 25 mm cannon. (Lockheed Martin)

Per the report:

F-35A gun accuracy during SDD failed to meet the contract specification. Although software corrections were made to the F-35 mission systems software to improve the stability of gun aiming cues, no software or hardware corrections have yet been implemented to correct the gun accuracy errors.

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Investigations into the gun mounts of the F-35A revealed misalignments that result in muzzle alignment errors. As a result, the true alignment of each F-35A gun is not known, so the program is considering options for re-boresighting and correcting gun alignments.

During air-to-air gun testing, F-35A operational test pilots received intermittent ‘unsafe gun’ cockpit alerts while attempting gun attacks. These alerts occurred with two different aircraft; the root cause is under investigation.”

Report: Air Force F-35's close air support gun doesn't work and only 60% of delivered jets fly
Firing the F-35A’s 25 mm cannon (USAF)

It is important to note that these issues plague only the internal gun permanently mounted inside the F-35A, which would be utilized by the Air Force for close air support missions. External guns mounted via pods to F-35B and C variants (Marine Corps and Navy, respectively) are said to operate up to required standards. The 25 mm cannon carried internally on the F-35A is affixed on the side of the fuselage and fires through a shutter that closes to prevent the gun’s presence from producing a radar return.