find more data sources
Options worth investigating:
- FAA ASDI (Aircraft Situation Display to Industry), 5 min delayed data for US & Canada.
- Aireon satellite.
- ADS-B Hub.
From what I've seen so far, none of the flight trackers offer live or even historical data over an API. I checked FlightRadar24, FlightAware, RadarBox. Maybe Plane Finder has one.