I raved last April about Flight+, a travel app from International Airport Flight Track Technologies. Flight+ diligently tracks every flight in the world, alerting you to delays and gate changes while relaying the current position of your chosen flight on a detailed map. It sends messages on changes to flight status, take off and arrival confirmations, as well as weather forecasts.
The app also contains flight displays for all major airports, gets seating charts for flights, and provides a world clock for keeping track of what's where and when. Flight+ comes in an iPhone or iPad version.
I've used it while traveling and waiting to meet a flight, and I can say it's the best travel app I've seen. Really, I've just touched on the extensive features in this post. If you travel at all, or have friends, family or business associates who do, this is a must-have app.
The paid, ad-free versions also have a fixed price cut: The iPhone version is now US$1.99 (previously $2.99) and the iPad app is now $3.99 (previously $4.99), starting today. Ad-supported editions are available as well. Either free or paid, I think you will like Flight+.