The default airport is Shenzhen Bao'an Int'l Airport (SZX).
Creating routes to and from this city with 747-8 to large cities such as London, Seoul, Tokyo, Los Angeles, etc. can get full occupancy and high profits. It's often recommended to start here as the city has very good ratings, but most players prefer nearby airports Hong Kong or Guangzhou. However, the city may attract moderate to heavy competition but can usually sustain it. Its locaton is advantegous for connecting to many major cities in China, India, etc.
Shenzhen Bao'an Int'l Airport will usually achieve a status of Level 6 or 7 by the end of the game. This makes the airport a bad choice for purchase as better options exist elsewhere. Additional airports should be left to the national government as they will rarely attain a status beyond Level 2 or 3.
On routes to medium-sized cities, planes such as the Boeing 757 and Airbus A340 are preferred. On routes to other large cities, planes such as the aforementioned 747 or the Airbus A380 are best used. Small planes should not be used as they will depreciate value.