The Japanese F-35 fighter jet missing in the Pacific could be a major security headache for the U.S. if Russia or China locate the state-of-the-art fighter jet first, experts warn.

Japanese defense officials say a search is underway for the fighter jet after it disappeared from radar during a flight exercise in northern Japan. The plane’s pilot is also missing.

Bristling with sophisticated technology and weaponry, the F-35 is the result of the most expensive weapons program in America’s military history, valued at $406.1 billion.

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“There is no price too high in this world for China and Russia to pay to get Japan's missing F-35, if they can. Big deal,” tweeted Tom Moore, a former senior professional staff member at the U.S. Senate Foreign Relations Committee.

Both Russia and China maintain a significant naval presence in the region, sparking concerns that they could find the missing F-35, Business Insider reports.

“If one of Japan’s F-35s is sitting at the bottom of the Pacific, we are probably about to see one of the biggest underwater espionage and counter-espionage ops since the Cold War. If it was operating without its radar reflectors pinpointing where it went in may be an issue,” tweeted Tyler Rogoway, editor of The War Zone.

“It could present problems depending on what is recovered, when it is recovered and, above all, in which conditions, after impacting the surface of the water,” Rome-based aviation expert, pilot, and former Italian Air Force officer David Cenciotti told Fox News via email. “The F-35 is a system of systems and its low observability/stealthiness is a system itself.”

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The F-35’s stealth is the result of the aircraft’s shape, its engine, the materials used to construct the plane and the “million lines” of software code used to manage its systems, added Cenciotti, who writes The Aviationist blog.

While the expert thinks that it would be difficult to reverse engineer the aircraft from pieces of wreckage recovered from the seabed, he warns that the debris could still offer vital information. “There are still lots of interesting parts that could be studied to get some interesting details: a particular onboard sensor or something that can't be seen from the outside but could be gathered by putting your hands on chunks of the aircraft intakes or exhaust section, on the radar reflectors etc,” he said

The stealth fighter, which has been beset by cost overruns and delays, has a price tag of around $100 million each. The U.S. Air Force, Navy and Marine Corps all have versions of the F-35.

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Japan’s Air Self-Defense Force says the F-35A stealth jet went missing Tuesday while flying off the eastern coast of Aomori. It says the plane disappeared from radar about half an hour after taking off from the Misawa air base with three other F-35As for a flight exercise.

Defense Minister Takeshi Iwaya told reporters that a search and rescue operation was underway for the missing jet and its pilot. The cause of the mishap was not immediately known.

Iwaya says 12 other F-35s at the Misawa base will be grounded.

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Japan plans to buy 147 U.S.-made F-35s, most of them F-35As, over the next decade.

The U.S. military temporarily grounded its entire fleet of F-35s last year after one of the jets crashed during a training mission in South Carolina.

Fox News’ Lucas Tomlinson, Travis Fedschun and The Associated Press contributed to this report.

Follow James Rogers on Twitter @jamesjrogers