How does Cirium source data?

For general information about how we collect data see here:
Data Innovation – Cirium 

Cirium employs industry standard processes and methods to source data from a variety of reputable providers for the creation of world-class proprietary products and services for use within the airline, aerospace and travel sectors. Relevant data is collected and curated from sources including, but not limited to, websites, governments, airlines, airports, manufacturers, and industry related organizations. Such data is collected using appropriate measures for obtaining the licenses, permissions, contributions and purchases required for the intended use of such data, as well as other lawful means of data acquisition via proprietary processes.

Further, any restricted data is carefully managed to ensure appropriate use in accordance with the applicable data use requirements. Such curated and formatted data is also used by Cirium within its products and services to create analytics using proprietary methodologies, programs and techniques for offering to its customers as standard online products and services.

How Cirium sources World Fleet data can be found here: 

https://helpdesk.cirium.com/hc/en-us/articles/360024623551-What-data-sources-are-used-to-track-the-world-s-fleet-