Preparing for a flight starts well before you arrive at the airport, and I don’t mean packing a bag.
Rather, most flights allow you to check in starting 24 hours before departure. And doing it right away (or failing to do so) can have big impacts on your flight experience, and overall costs.
For this reason, I check in as soon as the airline app or email tells me I can. It’s more than just securing my boarding pass; it’s a guaranteed way I can pay less on bag fees and sometimes get a better seat.
Just know that while the 24-hour opening is common for domestic U.S. flights, it’s not universal. Here’s what you need to know about seat assignments, upgrade lists, bag costs, and other deadlines that all come into play in the hours leading up to a flight.
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Your Seat Will Be Assigned at Check-in With Basic Fares
When you purchase a basic economy fare, you’re buying the cheapest ticket, and also the most restrictive one. Basic fares won’t let you select a seat for free when you buy your ticket. Instead, you’ll be assigned one by the airline at check-in, which typically begins 24 hours before a flight.
American Airlines, for example, automatically assigns a seat at check-in if a Basic Economy passenger has not paid an extra fee to choose one in advance, and it doesn't guarantee that companions will sit together. Its policy doesn't say that checking in earlier improves the assignment.
There’s also a strategy sometimes called “check-in chicken.” Instead of checking in right at the 24-hour mark, some travelers wait in hopes that other passengers will be assigned the less desirable seats first, leaving something better for those who check in later. It can work, but there is no guarantee the remaining options will improve. But if sitting together, avoiding a middle seat, or choosing a specific part of the cabin matters, you’ll want to opt to pay a fee to choose a seat ahead of time.
Upgrade Lists Appear, but Priority Starts Earlier
If you have elite status with an airline, check-in as soon as you’re able.
Elite status is a higher tier in an airline loyalty program that comes with extra perks, often including free upgrades on eligible flights.
On Delta, these travelers are called Medallion members. A complimentary upgrade means Delta moves an eligible passenger to a better seat or cabin without charging for it. Upgrades depend on your level of status and Medallion members can request an upgrade when booking, in the Delta app under My Trips, or automatically through their SkyMiles settings.
If Delta has not confirmed the upgrade by check-in, the request moves to the airport standby list. “Standby” doesn't mean you are waiting for a seat on the flight. Rather, you are only waiting to see if an upgraded seat becomes available. After check-in, you can see your place on the list in the Delta app, so it’s wise to check in right away to see where you stand.
Delta ranks passengers using factors including Medallion status, cabin type purchased, Million Miler status, certain credit-card and corporate-traveler priorities, and Medallion Qualification Dollars. Upgrade request time ranks eighth and only breaks a tie at the gate. Check-in time is not part of the ranking.
American Airlines works similarly: if an upgrade isn’t confirmed by check-in, the passenger keeps their original seat and stays on the airport upgrade list.
Bag Fees Can Change Before You Reach the Airport
Check in to your flight early and you could save on checked bag fees.
American and United both currently charge $5 less for each of the first two checked bags on many eligible routes when they are prepaid online instead of at the airport.
Other airlines price bags differently. Allegiant’s lowest bag price becomes available when you add luggage at booking, so waiting until check-in can actually mean paying more. Other airlines, like JetBlue, charge the same regardless of when you pay.
Before paying, check your airline’s policy and what your ticket already includes. Many premium cabins, airline-branded credit card, or airline status tiers may cover the cost of a checked bag. The better habit is to check the baggage policy when you book rather than assume the check-in screen will have the lowest price.
International Check-in May Trigger a Document Review
International check-in can turn into a document review, even if you’re doing it 24 hours before departure.
That’s because the time you check into a flight is also when the airline will confirm that you meet the entry requirements for the trip. A passport is standard, though a visa may be required depending on the destination, and some countries ask for proof of return or onward travel. If those details cannot be verified online, check-in may stop with instructions to see an airport agent.
I have had that happen. Flying from Atlanta to London Heathrow, my husband checked in online without a problem, while I was told to go to the desk. I was traveling on my Canadian passport and was a U.S. permanent resident at the time. I now had an extra step at the airport.
If this happens, bring the original documents required for the trip and leave time for a manual review. Missing the documents you need can mean being denied boarding.
The Check-in Window Closes Before Boarding Does
While a flight opening time gets most of the attention, the closing time can matter more. Online check-in, airport check-in, bag drop, and boarding can have different deadlines, so having a boarding pass doesn't mean every cutoff is behind you.
American is a useful example. Its online check-in closes 45 minutes before a domestic flight and 90 minutes before an international one. For airport check-in or bag drop, the general minimum is 45 minutes for domestic flights and 60 minutes for international flights, although some airports require more time, and boarding ends 15 minutes before departure.
Southwest and JetBlue follow the same pattern. On domestic flights, both require checked bags 45 minutes before departure; Southwest requires passengers at the gate 10 minutes before departure, while JetBlue requires them on board 15 minutes before departure.
Miss the applicable check-in minimum and your seat may be reassigned. Miss boarding and the flight can leave without you. I would save the earliest deadline that applies to the trip, especially when checking a bag or flying internationally, rather than treating the departure time on the ticket as the only one that matters.
The Shortcut
Pay to pick your seat if it matters. Basic economy gives you the assignment at check-in, and airlines claim when you check in during the 24-hour period doesn't matter.
Prepay your bags online depending on your airline. American and United knock $5 off on many routes, Allegiant is cheapest at booking, and JetBlue charges the same no matter when you pay.
International check-in is also a document check. If the airline can't verify your passport, visa, or onward travel online, it sends you to a gate agent.
