https://www.faa.gov/regulations_policies/orders_notices/index.cfm/go/document.information/documentID/1044857
Order 0000.1H - FAA Standard Subject Classification System
The Federal Aviation Administration is an operating mode of the U.S. Department of Transportation.
subject classificationorder00001hfaa
https://commons.wikimedia.org/wiki/Category:Classification_systems_by_subject
Category:Classification systems by subject - Wikimedia Commons
category classificationby subjectsystemswikimediacommons