While China's air force is gaining the edge over Taiwan's air force, the superiority is not so great that the Taiwanese won't be able to send aircraft against the invasion transports.
So China has a Plan B to protect the ships, deployed along their coast:
China now has eight battalions of S-300PMU2 anti-aircraft missile systems, on the coast opposite Taiwan. These missiles have a range of 200 kilometers, and are positioned to fire on Taiwanese fighters as soon as they begin to cross the 180 kilometer wide Taiwan straits.
Such missiles won't stop all attackers. And they won't affect Taiwan's ability to strike ships as they get closer to Taiwan with helicopters and aircraft.
But the SAMs do get the ships part way to Taiwan in relative safety and will reduce the damage they take when closer to Taiwan. it could be the difference between winning and losing a battle to make it ashore.
Those S-300s should be prime targets for Taiwanese cruise missiles.
