The Government Accountability Office released a report on Monday warning the Department of Defense against funding further software updates for the already $400 billion F-35 program until the current software becomes operational.

The F-35 is already operational with the Air Force and Marine Corps, but it runs a limited version of its software, called the 3i block, which only provides 89% of the code required for full warfighting potency.

Meanwhile, as the US keeps buying the jets, Lockheed Martin, the F-35’s primary manufacturer, is scrambling to provide 100% of the code with their planned 3F update.

At a conference earlier this year, Lockheed Martin told Business Insider they hoped to have the updated software loaded into the factory and ready to go on new jets by the end of 2017, but the GAO found that claim unlikely.