Hint :
To kill off the computers aircraft, build a big hill at
the end of his runway and cover with lots of trees.

Easy Money:
Start a new game, and before you build anything else, go to one coast and try to build a tunnel all the way through to the other. It doesn't have to go all the way; it just has to be really expensive. Instead of telling you that you don't have enough money, it gives you about 400 billion!