Can I assume it waiting for a button press or something from the user.
Yes, of course. Once all the initialization is done, the form shown, etc. the program does nothing but wait for the user to do something--unless you have an active timer or thread os something like that.
I assume there is nothing I can code after Load Airports to tell the program to go idle or park until called.
Not really, unless by "park" you mean going to
sleep() or something like that. If you mean just "idle, waiting for events" then the program is already in that state. You need do nothing more.
Incidentally, why don't you do all your
LoadXXX in the
OnCreate event? Unlike
OnShow,
OnCreate is guaranteed to be called just once in the life of the form, and by then all the design-time controls have been created already.