In what is probably the biggest case, FlightAware, a lot of the data comes from a fleet of users running ADS-B[1] receivers feeding data into their system.  ADS-B data is what Air Traffic Control uses to track planes, and it&#x27;s receivable using using a cheap TV tuner and a raspberry pi[2]. It ends up being probably the best way to track planes very precisely, as long as you can get enough coverage, which flightaware manages to do pretty well [3].  They then package this data and sell it via an API&#x2F;tools for Fixed Base Operators or apps like Just Landed.<p>[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Automatic_dependent_surveillance_%E2%80%93_broadcast" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Automatic_dependent_surveillan...</a>
[2] <a href="http:&#x2F;&#x2F;flightaware.com&#x2F;adsb&#x2F;piaware&#x2F;build" rel="nofollow">http:&#x2F;&#x2F;flightaware.com&#x2F;adsb&#x2F;piaware&#x2F;build</a>
[3] <a href="http:&#x2F;&#x2F;flightaware.com&#x2F;adsb&#x2F;coverage" rel="nofollow">http:&#x2F;&#x2F;flightaware.com&#x2F;adsb&#x2F;coverage</a>