(U.S. Navy photo by Lt. Cmdr. Darin Russell)

The US Navy has declared its F-35Cs ready for combat, but the service's own testing data says the stealth fighters designed to take off and land on aircraft carriers are nowhere close to ready, an independent nonpartisan watchdog reports.

"The F-35C is ready for operations, ready for combat and ready to win," Vice Adm. DeWolfe Miller, commander of Naval Air Forces, said in February 2019 as the Navy announced that the fighter had achieved initial operating capability. "We are adding an incredible weapon system into the arsenal of our Carrier Strike Groups that significantly enhances the capability of the joint force."


But the Project on Government Oversight, a nonprofit government-accountability group, warned March 19, 2019, that despite these claims, the F-35C, like the other variants, "continues to dramatically underperform in crucial areas including availability and reliability, cybervulnerability testing, and life-expectancy testing."

An F-35C Lightning II carrier variant joint strike fighter.

(U.S. Navy photo by Mass Communication Specialist Eli K. Buguey)

While still secretary of defense, Jim Mattis demanded last fall that the Navy and the Air Force strive to achieve a fleet-wide mission-capable rate of 80% for their fighters by October 2019. The Navy's carrier-capable F-35 variant is apparently nowhere close to that target, having consistently achieved unacceptably low fully mission-capable rates.

The mission-capable rates for the Navy's F-35Cs dropped from 12% in October 2016 to zero in December 2017, with figures remaining in the single digits throughout 2018, the oversight group reported, citing Navy documents. The US Navy, according to Military.com, also has only 27 of the required 273 F-35Cs, and the mission-capable rates do not apply to aircraft in testing, training, or depot.

"The fully mission capable rate for the full fleet is likely far below" the target set by Mattis, the watchdog concluded.

It said the Navy had opted to move forward with the aircraft "in spite of evidence that it is not ready for combat" and that it could "put at risk missions, as well as the troops who depend on it to get to the fight."

The group's analysis follows the release of a disconcerting report from the Defense Department's director of operational, test, and evaluation in January that called attention to F-35 readiness issues, such as life expectancy, cybersecurity, and stagnant aircraft availability.

Two F-35C Lightning II aircraft.

(U.S. Navy photo by Chief Mass Communication Specialist Shannon E. Renfroe)

"Fleet-wide average availability is below program target value of 60% and well below planned 80% needed," the official report said. "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."

The F-35 Joint Program Office responded to that report, saying the problems presented in the report were being "aggressively addressed."

The JPO told Business Insider that as of January 2019, the mission capable rate for the Navy's F-35C was 56 percent. "The Program Office has identified the enablers to increase our mission capability rates," a JPO spokesman explained.

"We will continue to learn and improve ways to maintain and sustain F-35C as we prepare for first deployment," the Joint Strike Fighter Wing commodore, Capt. Max McCoy, said as the Navy's carrier-capable variant was declared "ready for combat" February 2019. "The addition of F-35C to existing Carrier Air Wing capability ensures that we can fight and win in contested battlespace now and well into the future."

This article originally appeared on Business Insider. Follow @BusinessInsider on Twitter.