Radarbox.com is another flight tracking site similar to FlightAware, ADSB-Exchange and FR24. Instructions for feeding to Radarbox can be found at https://www.radarbox.com/sharing-data. Like most of the similar sites, feeding will get you an upgraded account for free. If you are already feeding others it is as simple as downloading and running a bash script.
Once you download and run the script a new repo will be added and their custom feeder app will be installed. Once their feeder starts running you can use sudo rbfeeder --showkey to see what your “key” is. A quick visit to the Radarbox website to create an account then “claim” your system at http://radarbox.com/raspberry-pi/claim and you are good to go.