Frequent fliers might want to download Flight Status ($4.99). It gives the status of thousands of flights, as well as the arrival gates and baggage carousels.
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Flight Status

Tracking the status of the flight is not always restricted to just the status of the flight. Very often, you also want to know the Airport status as well. 

Flight Status is the only application that provides you end-to-end information for your air travel. You can check Flight Status, Airport Status and also obtain information regarding the Airlines.  Flight Status app comes in two flavors - Flight Status & Flight Status Pro. Flight Status (available on AppStore for $4.99) is the complete flight tracking application for iPhone, iPad & iPod Touch. Flight Status Pro (AppStore link) application is also available as a universal app  and integrates with TripIt.

Flight Status works with thousands of flights from 1200+ Airline carriers around the world from 4200+ Airports.

Apart from checking the status of the flights, the 'Trips' module lets you group all flights you track in a trip from a single screen. This way, you can quickly get to the flights of your interest.

Flight Status Apps also support Push Notifications. This means, you need not manually check the status of the fight manually. You are notified when information about yout flight changes - like a gate change or delay. 

The data that is gathered and presented in the application is powered by FlightStats from Conducive Technology Corp. The data is processed and presented appropriately on our application. Flight maps are offered by FlightView.

Also, the application needs internet connectivity to gather this information. If you are traveling, roaming charges may apply.