Airport Classes

The class of an airport is determined by the population size of the city it is in. Each city name has a colored dot next to it to indicate it's class.  A class 1 airport will have a black dot and can only accept class one (smaller) planes.  Class 2 airports have a blue dot, are larger and can accept both class 1 and 2 planes. Class 3 airports have a red dot and can accept class 1,2 and 3 planes. Higher class airports not only accept larger planes but they also have more layover spots, more passengers/cargo that want to travel through them, and cost more coins to unlock. 

Check out the Airpedia for all of the planes and their classes.  You can also see an individual plane's class and other stats by clicking on the plane info button (icon with a plane and a magnifying glass).  To start with, you are given class 1 planes.  As you level up larger planes become available to you.

Region Headquarters: Requires Pocket Planes version 2.14.0 or newer.

In each of the six regions within Pocket Planes you can upgrade any chosen airport to convert it into a Region Headquarters (HQ). Each HQ is then considered a class 3 airport and holds up to 150 layovers (non-VIP) or 300 layovers (VIP).

To build a HQ, you upgrade the chosen airport until you see the Build Region HQ option. When the HQ is under construction you will send as many HQ related jobs to the airport as possible. Each HQ requires 1000 HQ jobs to finalise the upgrade (500 HQ materials and 500 HQ builders). The airport will be unlocked automatically once all 1000 HQ jobs have been delivered.