The Air FX can be set to free play however since there is no start button on the game the game will constantly run. To set the table on free play you enter the game programming mode and navigate to option P3. The value that you set for option P3 is the length in hours that the game will run, once the value is set save and exit the programming. When you would like to use the table power it on and press the "PLU5" button on the main board to start the table and initiate the count down of free play hours. .
ICE does sell a Free play button which can be added to the game. The ICE part numbers are AA2005, AA2052LX, and AA3062. With these three items you can add a free play button to the coin return slot and then interface the button harnessing with the games coin harnessing. Once this is set up you can program the game to 1 coin to start and press the button each time you would like to play the game.