Any town can go ahead and build an Airport or a Helipad inside their town claims, and ask one of the admins to make it functional by connecting it to the global airways.
Your airport should meet some requirements:
>Needs to be in claimed land
>Must be sealed of from the rest of the town to avoid infiltration
>(optional) An exit to the wilderness (people can exit the airport by using /t spawn as well)
5 emeralds is the standard fee for each flight. Travel from the plane is cost-free
Contact ChienAndalou or Monsquaz once these requirements have been met to install the warp sign