My wife's hometown (Chenzhou Hunan, 4.5 million, although just 1 million urban) just got an airport, so no more flights to Changsha or Guangzhou and then a 1-2 hour HSR connection into the city. I guess it seems a bit pointless, because HSR made the lack of an airport completely reasonable, but what do I know. But there are definitely enough people to justify an airport, like that airport in Guizhou...it serves 6.6 million people...so in 10 years they might think they didn't build it big enough.