One of the biggest reasons for flight delays in China is that the vast majority of the country's airspace is off limits to commercial aircraft.
As much as 80% of China's airspace is controlled by the military.
This is unusual. In many other countries, civilian aircraft are able to fly almost anywhere, while military-only airspace is limited.
The practical effect of the restrictions is that commercial flights are funneled through narrow corridors in China. This means planes fly farther than necessary, and delays are more likely to occur because of bad weather or heavy traffic.
While the military has begun to loosen some restrictions, it retains a firm grip on Chinese airspace.
Dramatic change will be difficult. China's military is not under government control -- it answers instead to the central military commission of the Communist Party.