Data from plane tracking.

People are finding different uses for aircraft tracking data.

https://www.bloomberg.com/news/articles/2019-07-02/hedge-funds-are-tracking-private-jets-to-find-the-next-megadeal

Where there’s a jet, there’s a data trail, and several “alternative data” firms are keeping tabs on private aircraft for hedge funds and other investors.

More power to them, and I am glad that my freely supplied data can make them money.
(Wow, that sort of sounded like a load of scorn… hehe).

Also; https://dictatoralert.org/
and; https://www.jettrack.io/