Originally Posted by
OskiBear
Probably because more time is involved in checking passports and ensuring passengers have the proper paperwork to travel on international flights?
Out of curiosity, do both China and Taiwan consider Cross-Straits flights to be domestic?
The cross-strait flights from Kinmen and Matsu to the island of Taiwan or Penghu are domestic - they are the only flights which are permitted to directly overfly the strait across the median.