In an episode of CBS' techno-procedural series CSI:Cyber that aired in January, pilots were forced to power off and power back on an airliner's flight computer to regain control from a hacker. As preposterous as that cold-boot of avionics sounds, it's something that test pilots have had to do with the F-35A "Lightning II" Joint Strike Fighter's radar system—not because of a hack but because of a software problem that causes the radar to degrade or stop working entirely.

IHS Jane's reports that an issue arose in late 2015 with the F-35's AN/APG-81 active electronically scanned array (AESA) radar system, built by Northrop Grumman for the Lockheed Martin-led F-35 program. The software planned to be used in the F-35A when the Air Force declares its "initial operational capability" (IOC) with the fighter later this year—revision 3i—has a major flaw. As Air Force F-35 Integration Office Director Major General Jeffrey Harrigian told Jane's, that flaw affects "radar stability—the radar's ability to stay up and running. What would happen is they'd get a signal that says either a radar degrade or a radar fail—something that would force us to restart the radar."

As several Ars readers have pointed out, rebooting an aircraft's radar system is not an uncommon occurrence. In the F-16, the radar had to be restarted with new code for different mission profiles. But the Air Force did not go into detail about when the instability in the radar system occurred, and clearly felt this was a problem worth shifting priorities to repair before IOC. Harrigan said that Lockheed Martin has discovered the cause of the problem and has diverted developers who were working on the next increment of the F-35's code to fix it. A patch is expected by the end of March. But if the fix is delayed, it could push back the Air Force's IOC declaration, which is currently expected some time after August of this year.

The Marine Corps gave the F-35B, the vertical take-off and landing version of the Joint Strike Fighter, an IOC declaration last June. The F-35B is running an earlier iteration of the software, and there have been no indications of a problem with the radar system in Marine aircraft.

The software version being run by the Marine Corps—Block 2B—contains what the F-35 office describes as "more than 87 percent of the required code for full warfighting capability." But it was plagued with other issues, and some tests were abandoned to get the software out in time for the June 2015 rollout. And the F-35B currently has a reduced number of weapons that it can be armed with because of missing software and integration work.