Online check-in opens 24–48 hours before departure in the airline's app or site; you get a mobile boarding pass. Go to the desk only to drop checked bags or if the airline needs to see documents (visas, some international routes).
When: most airlines open check-in 24 hours before departure (48 or more for some; low-cost carriers may charge for airport check-in). Set a reminder — good seats go early.
Bags: use the bag-drop desk or self-service kiosks; cutoffs are usually 45–60 minutes before departure.
Documents: for international flights the airline may require a document check at the desk (visa, ESTA, onward ticket) before issuing the pass, especially to the US, Australia and some Asian countries. Some apps verify passports digitally.
Mobile pass tips: screenshot it, add it to your wallet app, and keep the phone charged. Print a copy if your airport has weak signal or the app is flaky.
Related questions
How early should I get to the airport?
Two hours before a domestic flight, three before an international one, and add 30–45 minutes at mega-hubs, on holiday weekends, or if you're checking bags. PreCheck/Fast Track lets you trim about 30 minutes. Full answer →
What should I know before flying for the first time?
Check in online 24 hours ahead, arrive two hours early (three international), keep ID and boarding pass handy, pack liquids under 100 ml in a clear bag, follow the signs to your gate and be there when boarding starts. Everything else is optional. Full answer →
Airline, airport and government rules change without notice. Treat this as a starting point and confirm with the airline or authority for your specific trip. Request a correction if something is out of date.