Chadwick, Jr., William; Gorham, Jeff. Air Carrier Groupings 2019 — Directive No.328(PDF). Accounting and Reporting Directive of the Office of Airline Information (报告) 328. Washington, D.C.: Bureau of Transportation Statistics, United States Department of Transportation. October 1, 2018 [effective January 1, 2019] [2018-09-29]. (原始内容存档(PDF)于2018-09-29).
Chadwick, Jr., William; Gorham, Jeff. Air Carrier Groupings 2019 — Directive No.328(PDF). Accounting and Reporting Directive of the Office of Airline Information (报告) 328. Washington, D.C.: Bureau of Transportation Statistics, United States Department of Transportation. October 1, 2018 [effective January 1, 2019] [2018-09-29]. (原始内容存档(PDF)于2018-09-29).