Ryan you can get world of ai free http://www.world-of-ai.com/
it will work in fsx but you will have to disable aircraft shadows or the ai will be invisible due to how the airports were designed, its a temporary solution in till you get something like ultimate traffic 2 which was built and optimized for fsx.
It indeed will cost more money but it will be easer for you and you will have realistic ai. but it will effect your frame rates depending on how many planes are at the airport or /traffic density thats what most people run in flight simulator. or fellow Martins advice above.