Greetings to all of you. I go by Giantakeshi14 How Long Before a Delta Flight Can I Check-In? 24 hours before takeoff, registering for a Delta flight This covers flights both domestically and internationally. It is recommended that domestic travelers check in at least 30 minutes before takeoff and arrive at the airport at least two hours early. For international flights, arrive at least three hours early and check in one hour before departure. The online check-in window closes one hour and thirty minutes before domestic and international flights, respectively. If you check in early, you can guarantee easy travel.