If you are looking for a great flight-tracking piece of software, you can't go wrong with Flightradar24.
Flightradar24 gives you the ability to track flights and planes based on information such as flight number or destination, but it also offers a capability you won't find with most other flight tracking software. You can point your phone at a plane in the sky to find out its destination as well as what type of plane it is.
Other features of Flightradar24 include 3D views of what pilots are seeing, tracking flights around the world in real time, and the ability to see historical data on planes and flights.
Flightradar24 is free to use, but there are upgrades if you want even more information. Silver and gold subscription services give you more information and options.