Efficient check-in processes set the quality for a smooth travel experience. United Airlines MEX Terminal provides multiple options for check-in, including online check-in via the official website or mobile app, self-service kiosks at the airport, or traditional check-in counters. To expedite the process, it’s advisable to check-in online 24 hours before departure and arrive at the airport with ample time to spare. It is best to check in online 24 hours prior to departure in order to speed up the process, and make sure you get to the airport early.