Japan's military reported on Tuesday that it lost an F-35 stealth jet some 84 miles off the east coast of Aomori prefecture, Japan, in the Pacific.

Experts say Russia and China will do anything to get a look at the crashed jet, and if they do find it or can salvage it, they could seriously undermine the next several decades of US airpower.

Russia and China probably couldn't perfectly reconstruct the F-35, but any of its technology that ends up in the countries' hands would be a blow to the heart of the US military.

Visit BusinessInsider.com for more stories.

Japan's military reported on Tuesday that it lost contact with an F-35 stealth jet some 84 miles off the east coast of Aomori prefecture, Japan, in the Pacific and that the hunt was on for the pilot and the downed plane.

But if Russia or China — which both maintain a heavy naval presence in the region — find the plane first, the future of US airpower could be over before it started.

"Bottom line is that it would not be good" for the future of US airpower if Japan or the US don't quickly recover the jet, retired US Air Force Lt. Gen. David Deptula told Business Insider.

"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," Tom Moore, an expert on Russia and weapons proliferation, tweeted.

The hunt for F-35 tech is on

Lockheed Martin

Basically, if Russia or China, perhaps using their advanced and stealthy submarines to probe the ocean floor, first found the jet, they would gain a treasure trove of secrets about the most expensive weapons system in the history of the world.

The F-35 crash in the Pacific represents the first-ever opportunity for Russia and China to hunt for one of these planes in the wild because the jet has crashed only once before, and that time was on US soil.

Reverse engineering the technology could allow Russia and China to build their own versions of the jet, up to a point.

Read more: NATO will lose its next air war to Putin's 'formidable beasts' if it waits for the F-35 to save it

"The usefulness for Russia or China of recovering some or all of the wreckage would depend on how much damage the aircraft sustained upon hitting the water," Justin Bronk, a combat-aviation expert at the Royal United Services Institute, told Business Insider.

"The general shape of the jet is well-known, as are its performance characteristics so not much to gain there but parts of radar and other sensors would be prime targets for recover and testing/even attempts at reverse engineering," he added.

Russia specifically operates a fleet of shadowy submarines meant for very deep dives and research. The US and Japan have advanced maritime capabilities to search for the fallen jet but mostly rely on two of the US's aging rescue and salvage ships and on large nuclear submarines, which may not be ideal for the rescue mission.

Read more: Russia says it's going to arm a submarine with 6 nuclear 'doomsday' devices

As of now, all anyone knows is where the F-35 was last seen flying. It could have continued on for miles, and currents may have dragged it miles farther. In short, the entire region has a chance at brushing up against some piece of it.

What Russia and China stand to gain

Russia and China know what an F-35 looks like. There's even some evidence China stole plans for the F-35. But even with an F-35 in its hands, the two countries still lack the advanced manufacturing know-how held in the US.

Just having some composite material used in the F-35's jet engines wouldn't necessarily allow China to create the materials at will. Just measuring the characteristics of the fuselage wouldn't necessarily allow Russia to reliably manufacture airframes like the F-35's on its own.

Read more: The US is ready to send in F-35s into combat if tensions with Russia and Syria boil over

The F-35's stealth and performance represent a tiny portion of its worth to the US military. The rest lies in the networking, sensor fusion, and secure communications.

There, according to Bronk, the jet stands a chance against prying eyes.

"Samples or the 'fibre mat' stealth coating would be sought after," Bronk said. "But the jet’s all-important software and programming would likely be hard to reconstruct given not only the likely damage from the crash and salt water in Pacific but also the way that the jet’s sensitive systems are designed to be very hard to decipher and reverse engineer to make it more suitable for export."

Despite the US's best efforts, Russia or China salvaging any part of the F-35 represents a US security nightmare.

"Both China and Russia have excellent reconstruction/reverse engineering/copying skills, particularly the Chinese as they are masters at it," Deptula said.

Bronk and Deptula both agreed that in Moscow, Washington, Beijing, and Tokyo, the race is now on to find the fallen F-35 to either protect or undermine its future as the lynchpin of US and allied airpower.