Flightradar24

The most famous flight tracking application in the world, Flightradar24, has a version for Android that lets you see commercial planes and their flight routes at any time.

This application lets you identify every flight that appears on the screen. However, in this demo version, you can't see the time of departure or arrival, nor the destination or origin of any flight. You can only see the plane's model.

You'll see all the planes in real-time, and you'll be able to search for specific flights, as well as zoom in anywhere on the map to see with absolute clarity the flight routes that connect different countries and continents.

The full version also gives you the possibility of filtering your search by altitude, airline, and speed. The trial version doesn't leave any flight out, though, so you can still see all of them.