National security angle is also often overlooked. China is not self sufficient in airplane manufacturing. Not now and back then it was only a plan.

What would they do in case of airplane export ban? They could keep existing ones airworthy, but transport capacity would be capped.

High speed trains are a viable alternative to airplanes.

China has the C919 (equivalent to a Boeing 737 or A320), which still relies on imported engines, but the country is also developing its own jet engines for commercial use. They would accelerate those efforts if there were an export ban.

Except for a couple of lines that connect the megacities of Beijing, Shanghai, Guangzhou and Shenzhen, most Chinese HSR lines operate below capacity and at a great loss.

The bulk of the rail built in the last decade was to distant poorer regions who simply aren't willing to pay for faster transit.

If a line is operating at capacity, that's a problem. That's when you start getting overcrowding and delays. Overall utilization rates of Chinese HSR lines are fairly high. Less than 100%. More than 50%.

> to distant poorer regions

Rail is also used as a tool for economic development of such regions. The US built interstate highways across vast stretches of empty land, because the idea was to have a national grid that benefits the entire country.