The Pentagon has announced that its super expensive and troubled Lockheed Martin F-35 jet fighter will serve additional six years before fully retiring by 2070. However, experts warn that it will take Russia and China a lot less time to design and manufacture aircraft that are superior to the Joint Strike Fighter.

US military officials have already acknowledged that Russia and China are developing planes at a much faster rate than they anticipated. Lt. Gen. James Holmes, Air Force deputy chief of staff for strategic plans and requirements, told the US Senate Armed Services Committee as much earlier this month.

In fact, both countries could have already closed the technological gap, defense analyst Dave Majumdar wrote for the National Interest. "Over the next half-century, the Russians and Chinese will almost certainly develop ways to counter the F-35 — indeed, there are indications that they already have," he noted.

Col. Mike Pietrucha shared this sentiment.

"We have been technologically outmaneuvered by both Chinese and Russian air defense designers, as we double down on a technology that gave us a decisive advantage a quarter century ago," he wrote for the War on the Rocks website. "We are building the combat air force for the wrong attributes, and we are unlikely to reconsider this path as long as the Air Force remains stuck in denial."

© AP Photo / LM Ottero Lockheed Martin F-35 Joint Strike Fighter

This could be the latest in a string of bad news for the Joint Strike Fighter program, which has been in development for more than two decades. Last week, reports emerged that the F-35 will not become combat ready until at least 2022, although it was supposed to be fully operational in the early 2010s.

Majumdar described the "F-35 goliath" as a sixty-year program with unpredictable costs. The program, according to estimates, has already cost $1.3 trillion and counting.