NATIONAL HARBOR: China‘s air force is laboring mightily to improve both its planes and its personnel — causing much American concern– but it has a long way yet to go.

The People’s Liberation Army Air Force (PLAAF) is becoming “much smaller but much more technologically sophisticated,” said Phillip Saunders, director of the Center for the Study of Chinese Military Affairs at National Defense University, in a talk Monday afternoon at the Air Force Association’s annual conference here.

The PLAAF has shed squadron after squadron of geriatric jets, mostly Chinese copies of old Soviet designs like the 1950s-vintage MiG-19 and MiG-21. Meanwhile it has invested in building up the world’s third-largest fleet of so-called “Fourth Generation” fighter aircraft: the Russian Sukhoi Su-27 and Su-30, the Chinese copy called the J-11, and the homegrown — with Israeli assistance — J-10 (pictured), considered roughly on par technologically with America’s mainstay F-15s, F-16s, and Navy F-18s.

China is also experimenting with “fifth-generation” aircraft that supposedly will have stealth capabilities comparable to the new F-22 and F-35: the large J-20, provocatively unveiled last year just as then-Secretary of Defense Robert Gates visited China, and a smaller one variously called either J-21 or J-31, unveiled last week during Secretary Leon Panetta’s visit. (No messages here from the PLA. No. Of course not.)

It’s important not to exaggerate the Chinese threat. Their stealth planes are mere “prototypes,” Saunders emphasized, in contrast to US fifth-generation fighters actually in production (however troubled), while even China’s growing “fourth generation” fleet is badly outnumbered by the US.

What’s more, Saunders, said, while China’s capabilities have been advancing rapidly, it is beginning to hit real limits. The Russians are sick of the Chinese stealing their technology, so they are cutting back on cooperative ventures, particularly guarding their engine manufacturing, which China cannot reproduce. The US and Europe have never lifted the arms embargo imposed after the Tiananmen Square massacre of 1989. Even the Israelis, China’s long-time backdoor to Western technology, have been less cooperative.

As a result, “we see an increasing emphasis on espionage,” Saunders warned. “It’s been publicly reported that there have been cyber attacks on US aviation manufacturers, that a lot of design information has been stolen, [and] that’s likely to continue,” he said. “There’s a demand and a need in China to acquire technologies this way.”

As important as the technological tools, however, is the people who wield them. Chinese pilots historically trained to fly mainly in daylight and good weather, over land. In recent years, however, Saunders has seen “much more emphasis on realistic training,” including at night, in bad weather, and even over water — which will be essential to projecting Chinese airpower in a future conflict over Taiwan, the Daiyou Islands disputed with Japan, or the South China Sea.

On the ground, the Chinese still lack a corps of professional non-commissioned officers, so key functions like maintenance remain dominated by commissioned officers — who are still mostly graduates of military academies that offer only the equivalent of a two-year associate’s degree. But the PLAAF has made a major push to recruit more officers from China’s civilian universities, as well as founding new professional education institutions for officers already in the ranks.

When Chinese military delegations visit National Defense University, today, Saunders said, “the quality of those officers is much higher, much more sophisticated, than it was even four or five years ago.” That is arguably the most important improvement in the Chinese military — and the most ominous development for the US.