Classified F-35 Canopy ends up in China.

At first glance, an F-35 canopy may not sound like a major intelligence prize.

It isn't the radar, mission computer, electronic warfare system or source code, but on a fifth-generation stealth fighter, there really isn't such a thing as “just a canopy.”

A shipment of unserviceable F-35 components being transported from Australia to the United States was mistakenly diverted through Hong Kong. The shipment reportedly included a cockpit canopy and a weapons-bay door, with at least some of the components ending up in Chinese hands.

Officials have described the parts as non-sensitive. That doesn't mean they aren't useful.

The F-35 canopy is part of the aircraft's low-observable system. A conventional fighter cockpit can be a major radar reflector as energy passes through the transparency and bounces off the pilot, ejection seat, displays and other hardware inside.

The F-35 reduces that problem through specialized conductive coatings, materials and precise manufacturing.

Give a sophisticated laboratory an actual canopy and engineers can do much more than look at photographs.

They can measure coating thickness, identify materials, examine layering, study edge treatments and sealants, and test how the canopy responds to different radar frequencies and angles.

That doesn't mean China can suddenly copy an F-35. Stealth isn't a magic paint. It is the combination of aircraft shape, coatings, manufacturing tolerances, weapons carriage, antennas, engine shielding and electronic systems, but a canopy provides another piece of the puzzle and China may not even be interested primarily in copying it.

The more important question may be: What can it teach them about detecting an F-35?

If Chinese engineers can characterize how the canopy absorbs and reflects radar energy, they may learn where the cockpit contributes to the aircraft's overall radar signature, which frequencies the material performs best against, and where compromises had to be made for visibility, durability and structural strength.

That information could potentially help improve Chinese radars, sensor networks and detection algorithms.

The weapons-bay door could be equally interesting. Doors, seams, hinges and panel interfaces are critical on stealth aircraft because tiny discontinuities can create radar reflections.

Physical hardware allows engineers to see exactly how American designers dealt with those problems.

It could also help China's own stealth programs.

With the J-20 already operational and additional low-observable aircraft under development, American components provide a valuable benchmark.

Chinese engineers can compare U.S. coatings, materials, tolerances and manufacturing techniques against their own.

One of the biggest unanswered questions is how old these parts were.

If the canopy was an early-production, heavily used component headed for disposal, its intelligence value may be limited.

If it represented a more recent production standard, that would be considerably more interesting.

Either way, the incident highlights an important distinction:

Unclassified does not mean useless.

An F-35 canopy won't teach China how to build an F-35.

But give one to a room full of Chinese radar engineers, materials scientists and stealth specialists, and you can bet they'll study every square inch of it