f you don’t check in 24 hours before your flight, you may still be able to board, but it can lead to some problems or delays. Most airlines open their online check-in window exactly 24 hours before departure, and it usually stays open until around 45 to 60 minutes before the flight. This window gives travelers a chance to confirm their booking, choose or update seats, and get a boarding pass in advance. If you skip this step or forget to check in online within that time, you’ll need to check in at the airport counter or self-service kiosk on the day of your flight. While this is still an option, it may take longer and add extra stress, especially during busy hours.

One of the main issues with not checking in early is limited seat availability. Many passengers use early check-in to select better seats, such as window or aisle spots. If you wait too long, you may only get leftover seats, often in the middle or in less comfortable areas of the aircraft. On full flights, the airline may reassign seats for passengers who haven't checked in, and you could even risk being bumped from the flight if it’s oversold. Airlines generally give priority to passengers who checked in on time, especially for lower fare classes or standby travelers.

Arriving at the airport without having checked in can also result in longer wait times. When you check in online, you skip the main line and can go straight to the security check if you have no baggage. But if you didn’t check in beforehand, you will need to wait in line at the counter, which could delay your journey, especially if the airport is busy. This is even more stressful if the airport has long security lines or your boarding gate is far from the check-in area.

If you're traveling internationally, checking in late can be more risky. Airlines often need to verify your travel documents, such as your passport, visa, or vaccination proof. If you don’t check in early, you might run into time pressure at the airport if those documents need to be reviewed. In worst-case scenarios, missing this step or arriving too late can cause you to miss the flight entirely.

Some low-cost or basic economy fares may have even stricter check-in rules, and late check-in might result in fees or penalties. If the check-in deadline passes before you get to the counter or kiosk, your seat might be released, and you may have to pay to rebook or wait for the next flight. Not checking in on time can also limit your ability to receive important flight updates, such as gate changes or delays.

In conclusion, not checking in 24 hours before your flight doesn’t always mean you’ll miss your flight, but it can lead to limited seat choices, longer lines, extra stress, and the risk of being denied boarding. To make your travel smoother and easier, it’s always best to check in as early as possible.