You can earn coins in the following ways:
— Collect profit from airplane and helicopter flights
— Collect profit from space launches
— Collect profit from commercial buildings in your airport and neighboring cities
— Get coins for completing collections
— Enter gift codes published on Facebook (https://www.facebook.com/AirportCity/)
— Get coins for completing various exciting quests from the Quests section; you can find the daily quest icon on the left side of the screen
— Get coins for event progress
— Buy coins from the Bank.