| https://lssds.noirlab.edu/winter_school/sites/default/files/American-Airlines-Refund-Policy.pdf |
| https://lssds.noirlab.edu/winter_school/sites/default/files/can-i-cancel-my-flight-and-get-a-refund-on-american-airlines.pdf |
| https://lssds.noirlab.edu/winter_school/sites/default/files/what-reasons-qualify-for-an-aa-refund.pdf |
| https://lssds.noirlab.edu/winter_school/sites/default/files/what-is-the-45-minute-rule-for-american-airlines_0.pdf |
| https://lssds.noirlab.edu/winter_school/sites/default/files/united-airlines-refund-policy.pdf |
