FlightView is a cool app that costs too much for regular users. The $4.99 app gives you the ability to track upcoming and in-air flights. You can even view a map of where the plane is currently. You also get notifications when the flight status changes and it is all integrated into the BlackBerry calendar.
The convenience of the app may be worth it for regular flyers but for most people you can just use one of the multitude of free websites or even Google to check flight stats. Many sites like FlightStats offers free email or SMS notifications on flights you are tracking. Other agencies like Orbitz will send you messages or even call you for free.