Taiwanese papers revealed on Monday that a Chinese spy plane patrolled the island’s air border just as the self-governing territory began an annual war-game exercise aimed at preparing for an invasion from China.

The Han Kuang exercise has been held annually since 1984, and is devised to train the Taiwanese army how to react in the event of an attempted military takeover by Beijing.

The Chinese aircraft was identified as a Y-9JB, the electronic warfare variant of the Y-9 medium-sized airlifter.

The spy plane flew over the East China Sea to the West Pacific through the Miyako Strait and proceeded south to the Bashi Channel before returning home, along the way triggering an interception after Tokyo scrambled its fighter jets.

Taiwan’s defense ministry said it monitored the plane throughout. They claim it was attempting to monitor radar systems parameters at a time when the Taiwanese military’s mobilization for the Han Kuang exercise was in full force.

The ministry said it could not rule out further breaches of Taiwan’s airspace by Chinese warplanes as the Han Kuang exercise proceeds.

The focus of the first two days of the exercise will be the marshaling of air force and navy units to brace for imminent Chinese aggression.

Taipei’s contingency plan involves several squadrons of the F-16 and Mirage 2000 fighters normally used to patrol its western front facing China. They, along with mission-critical spare parts, will be flown to key underground hangers in Hualien County on Taiwan’s east coast to preserve aerial combat power for protracted resistance.

On the ground, Taiwanese troops engaged in live-fire exercises along the Tamsui River on the outskirts of Taipei. The operation involved CM-11 tanks, FGM-148 Javelin anti-tank missiles, as well as CM-21 armored personnel and CM-22 mortar carriers, Taiwan’s Central News Agency reported.

The river is seen as a natural bulwark in the defense of the Taiwanese capital against the advancement of a People’s Liberation Army spearhead that is anticipated to include paratroopers and amphibious forces.

In a separate development, China’s Air Traffic Management Bureau has issued a notice cordoning off a flight zone from sea level to an indefinite altitude, for a “spaceflight” that they claim will take place west of the centre line of the Taiwan Strait between 9pm and 9:59pm Wednesday evening.

Some suspect that the no-fly ban was issued because a spacecraft could be falling from its orbit.

So far there is no more information available about such “spacecraft”.