Japan's air force faces a 'relentless' burden, imposed by China

More than twice a day, Japanese fighter pilots hear a siren blare, bolt up from their ready-room seats, run to their jets, and scream aloft, ready to intercept a potentially unidentified incursion into Japanese airspace.

It happened to Japan's Air Self Defense Force (JASDF) 947 times in the last fiscal year ending in March. The culprit in most of those cases, warplanes from China's People's Liberation Army Air Force (PLAAF).

And Shirota says the number of potential incursions is growing.

"The number of scrambles against airspace violations has been increasing rapidly over the past decade -- especially in the southwest air zone," said Shirota in an exclusive interview with CNN. "About 70% of the scrambles done by Japan's SDF annually are conducted in this area."

That southwest area includes the Senkaku Islands -- known as the Diaoyu Islands in China -- a rocky, uninhabited group of islands under Japanese administration but claimed by China as its territory.

It also includes Okinawa, home to the United States Air Force's Kadena Air Base, which touts itself as the "Keystone of the Pacific" and is a key US installation for flights over the contested waters of the South China Sea.

Japan's Defense Ministry in March released a map showing the flight routes of Chinese and Russian aircraft that Japan's fighter pilots rose to intercept. The Chinese flight routes are shown in red. Their density makes the East China Sea, the part of the Pacific Ocean between China and Japan's southern islands, look like a sea of red.

The Chinese flights don't violate international law. Of the 675 times Japan's fighters scrambled after Chinese planes in the last fiscal year, not once did the Chinese aircraft fly within the internationally recognized 12-mile territorial limit, according to the Japanese Defense Ministry.

And even then, China says the presence of its forces within the Senkakus/Diaoyu island chain is within its sovereign rights.