GOG install instructions:
Make sure before clicking "INSTALL NOW" that you have downloaded the setup files from your GOG library after purchase, into your download folder, so Porting Kit can start the installation automatically. You will be prompted to install the game like if you were in Windows.
On this page you find the native Mac game Airline Tycoon Deluxe This is no game port, but the native Mac version of the game. There is no Porting Kit required to play the game and this page only directs to the Native Game page on GOG.com, where you can purchase the game, download it, and play!
Airline Tycoon Deluxe is a funny economy simulation proceeding in realtime and assigning you the complete responsibility for an airline. However, don’t be fooled by the funny comic style or the included jokes: A variety of tasks are requested and your competitors never miss a chance to set a trap for you in order to put a spoke in your wheel.
This is a native game from GOG.com.