For online check-in for an AeroMexico flight, go to their website or mobile app, enter your booking reference or ticket number, and then follow the on-screen instructions. Alternately, get to the airport early, look for the AeroMexico check-in counters or kiosks, and ask someone there with your reservation information or passport. As online check-in often opens up 24-48 hours prior to departure, make sure you have all appropriate travel documents. Check AeroMexico's recommendations for your specific airport and destination since they may have specific rules that apply.