ADSBexchange.com, a co-op of ADS-B/Mode S/MLAT feeders from around the world is the world’s largest source of unfiltered flight data. Thanks to the worldwide community of participants, if the data is broadcast over the air, you can find it here.
Various Filters are allowing the User to show exactly the Map and Plane that he needs. Especially the Mitlitary Enthusiasts will be finding this the most important App to use.
For PC: https://global.adsbexchange.com/VirtualRadar/desktop.html