Why can't I check in online? The possible reasons explained

Times

21-05-2025

Part of the ritual of a holiday flight is getting to check in online before you go to the airport. It's that window of opportunity where you can choose your preferred spot — ideally swerving the toilets and the squeezed middle seat. But once in a while you'll get a notification to say you have to check in at the airport instead, and no matter how many times you try, the system just won't budge. Your mind might flicker to the worst-case scenario, but there's often a simple reason for it.
Flights are often operated on a codeshare basis, which means the airline you booked with might not necessarily be the one you're flying with.
So while you might get an email asking you to check in, you won't be able to do it on the website of the airline you booked with — instead, you'll need to check in via the website of the airline operating the flight.
Look through your emails: there's usually a second booking reference somewhere that mentions the codeshare partner, and this is the one you'll need to use on the codeshare partner's website.
Glitches on websites and apps happen all the time, whether through human error, a system update or incompatibility with your device.
If you're denied online check-in, it might be worth retrying a few hours later or on a different device. Sometimes, you might find that you're able to check in online using a laptop, but not your phone or tablet.
Airlines often oversell flights so that when passengers fail to turn up, or switch their booking to another date, they have spares to fill up those empty seats.
The downside, of course, is that when everyone does show up there aren't enough seats — so they have to bump some passengers on to another flight. So if you can't check in online, it may be a sign that you're being held back.
In some cases, a space can become available at the last minute, which is why you're then able to check in at the airport as if nothing's happened.
Apart from an overbooked flight, there are lots of operational reasons why there are no longer enough seats available.
This might include a change of aircraft, meaning that there are now too many passengers, or that some pre-allocated seats are no longer available. You may also be bumped from the flight to allow crew on standby to travel instead.
For long-haul destinations, especially flights to the US, you often need to fill in additional passenger information before you travel.
In the case of the US, for example, this includes whether you're travelling on an Esta or a visa, and where you're staying. Some destinations will also require you to submit your passport details before you travel.
It's always worth checking whether you need to submit any additional documents or information after your booking, as it may be too late by the time you check in.
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Depending on your destination, airlines may need to carry out additional checks, such as whether you have the right visa or if your passport is still valid, which can only be done in person at the airport. This applies to all passengers.
In some cases, you might be singled out for additional checks because you've been flagged as suspicious.
Reasons might include: if you have more than one passport, if you're a certain nationality, if your flight was booked at the very last minute, if your flight was booked by someone else, or if you have the same name as a person of interest.
And if you're travelling alone with children, you might also be flagged if you have a different surname to them. You'll need to carry additional documents, such as a birth certificate and letter of consent from the other parent, to satisfy border concerns around child abduction and trafficking.
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