Really great game - normal price is $.99...I have had this on my phone for a few years and it is very addicting and a great time waster (especially when sitting on a plane).
The HD iPad version is also free at the moment.
"Air traffic control is the world's most stressful job, but not for you. You don't need heading angles, flight rules or meteorological reports, you're a natural! A prodigy! A born controller!"