Https://mechatronics.ucmerced.edu/sites/g/files/ufvvjh1226/f/webform/how-early-should-i-check-in-for-a-southwest-flight-clear-action-guide.pdf https://mechatronics.ucmerced.edu/sites/g/files/ufvvjh1226/f/webform/how-early-should-i-check-in-for-a-southwest-flight-clear-action-guide.pdf