https://collaboratory.gse.upenn.edu/sites/default/files/webform/af-flightedit-can-you-change-an-air-france-flight_0.pdf
https://collaboratory.gse.upenn.edu/sites/default/files/webform/%E3%80%90af-ticketrules%E3%80%91what-is-a-changeable-ticket-on-air-france_0.pdf
https://collaboratory.gse.upenn.edu/sites/default/files/webform/af-feeavoid-how-to-avoid-air-france-change-fee_3.pdf
https://collaboratory.gse.upenn.edu/sites/default/files/webform/iberia-modifybooking-can-i-change-my-iberia-flights_1.pdf
https://collaboratory.gse.upenn.edu/sites/default/files/webform/%E3%80%90Iberia-FlightUpdate%E3%80%91Can%20you%20change%20flights%20with%20Iberia__0.pdf
https://collaboratory.gse.upenn.edu/sites/default/files/webform/iberia-24hourcancel-does-iberia-give-you-24-hours-to-cancel_1.pdf
https://collaboratory.gse.upenn.edu/sites/default/files/webform/%E3%80%90iberia-changedesk%E3%80%91does-iberia-allow-flight-changes_0.pdf
https://collaboratory.gse.upenn.edu/sites/default/files/webform/%E3%80%90ana-changepolicy%E3%80%91-does-ana-let-you-change-flights_0.pdf
https://airlinedirectconnect.zohodesk.com/portal/en/kb/articles/american-help-is-it-free-to-change-flights-on-american-airlines
https://airlinedirectconnect.zohodesk.com/portal/en/kb/articles/flight-help-how-do-i-change-my-american-airlines-flight