Flighty is a free app for iOS (it's not available for Android right now) that's slowly growing on me.
Unlike some of these other popular flight tracking apps, Flighty has a nice, clean user interface that's easy to navigate.
Flighty will also monitor delays by tracking your inbound planes for 25 hours prior to your flight. It also tracks FAA mandated delays.
The app also features pilot-level data including real flight maps, live tracking, tail number details, and a wealth of other information.
It also integrates nicely with TripIt, email forwarding, and Calendars.
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