On Southwest Airlines, boarding position is determined by check-in order — checking in at exactly 24 hours gets you a better seat. On other airlines, early check-in reduces the risk of being bumped on oversold flights and ensures you get your preferred seat.

Use the local time at your departure airport. If your flight departs at 3:00 PM from Chicago, enter 3:00 PM regardless of your current location. The check-in window is based on the scheduled departure time.

No. Airlines' systems will not allow check-in before the window opens. The timer on this page helps you be ready at the exact moment check-in becomes available.

You can still check in at the airport counter or kiosk. However, on budget airlines like Ryanair, missing online check-in may result in a fee (€/£55). On full-service airlines, there's no penalty — you just lose the advantage of early check-in.