(CNN) - A technical issue may force the military to ground 2,500 of the world's most advanced warplanes.
A new report by the Government Accountability Office says the problem is with the software, or brains, of the military's F-35 Joint Strike Fighters.
The federal watchdog group warns a failure could take the entire fleet offline due in part to the lack of a backup system.
GAO says not enough testing was done to ensure the software will work properly.
The upgraded planes were expected to be ready for deployment by 2017, but the GAO says it’s not clear if the integral software component of the weapons system will even be ready by 2019.
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