Https://mechatronics.ucmerced.edu/system/files/webform/fasthelp-what-happens-if-you-dont-check-in-24-hours-before-your-flight.pdf https://mechatronics.ucmerced.edu/system/files/webform/fasthelp-what-happens-if-you-dont-check-in-24-hours-before-your-flight.pdf