In Airport City, we use Stands instead of hangars. Stands serve as maintenance zones for planes. When a plane is at a Stand, it's in a waiting area for its flight. During this time, the plane gets refueled, boards passengers, and returns after the flight is complete.
Stands are versatile and can provide services for all types of planes, from Swallow to Condor, including both your own planes and those of your guests.
Please keep in mind that you'll need an available Stand to receive a guest plane. You can either reserve a Stand specifically for guest planes or use any open Stands when your planes are on flights.
The number of Stands you have access to depends on your level. However, if the Control Tower's level doesn't allow you to purchase an additional plane, you won't be able to build another Stand either.