https://www.brookings.edu/wp-content/uploads/2021/08/AI-report_Full.pdf
http://ec.europa.eu/transport/sites/transport/files/eu_air_carriers_by_country_holding_an_active_operating_licence.pdf
https://eur-lex.europa.eu/legal-content/FR/TXT/PDF/?uri=CELEX:32019R0452&from=EN
https://www.cesifo-group.de/DocDL/ifoDD_18-01_29-31_Achten.pdf