Airport City: What do I need Control Tower for?

The Control Tower is responsible for the maximum number of active planes at your disposal. Active planes are all the planes you are using at the moment included those in flights, staying in Aprons or waiting for repair. Those planes in Reserve Hangar are not counted among your active ones.

Note that if the Control Tower level does not allow you to purchase another plane, you won’t be able to build another Stand either, although the maximum number of Stands depends on your level.