Turns out there are lots of ways that aircraft communicate with the ground and that ground uses to track aircraft - like radar and transponders. I have been digging into ADS-B which aircraft use to transmit basic data like GPS location, altitude and air speed. The interesting this is that ADS-B signals are transmitted "in the open" over VHF 1090 MHz.
Long story short - I setup my own receiving station using FlightAware PiAware. It's solution running on Raspberry Pi and a USB receiver that translates the raw radio signals to data. The whole thing is packaged up by FlightAware and they make it super simple to get it up and running.
I have been hacking around trying to get my own Python script to pull the data just to play; but it way more fun just to watch.