Checking in online 24 hours before your flight leaves gives you the opportunity to select your seat and print out boarding passes ahead of time. This will save you time at the airport and make sure that everything runs smoothly on the day of travel.

Checking in 24 hours before a flight serves two critical purposes: airline logistics and passenger commitment. For the airline, it provides a final count of "show-up" passengers, which is vital for calculating the aircraft's weight, balance, and fuel requirements. It also allows them to manage "oversold" flights; if fewer people check in than expected, they can release seats to "standby" travelers or those on a waiting list. For the passenger, the 24-hour mark is often the moment you can secure your seat assignment, pay for bags, or verify travel documents like visas. In 2026, many airlines use the check-in process to prompt you for mandatory health or security declarations. If you miss the check-in window (usually closing 60 minutes before departure), the airline reserves the right to cancel your reservation and sell your seat to another traveler.