When You Check in for a Flight Matters—Here’s Why

Prior to the advent of the Internet, passengers used to have to wait until they were at the airport to check in for their flights. Sounds prehistoric, right? Fortunately, these days, most airlines allow you to check in online, starting at least 24 hours before your flight departs. In fact, they’ll even send you emails and texts reminding you to do so. Still, many passengers who are accustomed to checking in at the airport ignore these alerts. Why check in online so far in advance, especially if you have to visit a counter anyway to check a bag? It turns out there are several reasons you should check in early.

Ideally, you can pick your seat for free when you purchase your flight, but that’s usually not the case if you’re flying coach. If you want to save money and are willing to risk getting a middle seat, your seat will most likely be assigned at check in. In most cases, the earlier you check in, the greater your chances of scoring a window or aisle seat. Some airlines, especially if you’re flying on an international itinerary with different airlines, don’t allow you to choose a seat—even if you’re willing to pay for it—until check in. In that case, the sooner you check in, the sooner you can pick one.

Furthermore, according to the U.S. Department of Transportation, airlines are allowed to oversell flights, within reason, to compensate for no-shows. If there aren’t any no-shows, and the plane is overbooked, the airline is allowed to bump passengers to a later flight. One of the criteria they sometimes use to determine who gets bumped is check-in time. If you checked in last, you may be the first to be bumped.

A spokesperson for Delta tells Travel + Leisure that checking in early in person is also essential if you’re checking a bag. “For most U.S. airports, when traveling domestically, baggage must be checked in at least 45 minutes before scheduled departure time.” If you’re flying domestically without checking a bag, you only have to be checked in 30 minutes prior to departure. Why the extra 15 minutes for passengers who want to check a bag? Before your bag is loaded onto the plane, it has to be sorted and go through TSA screening. If you check in after the 45-minute cutoff time, you can still board the flight, but your bag probably won’t make it, and there’s a good chance you’ll have to leave it behind. For international flights, you have to check in even earlier—at least 60 minutes before your scheduled departure—if you’re checking a bag.

Check-in cutoff times vary by airline, so it’s important to be familiar with your airline’s policy. You should also look up the requirements for the airport you’ll be flying out of. According to the Delta spokesperson, some airports require passengers to check in even earlier than the airlines do. For example,  if you’re flying domestically out of JFK and are checking a bag, you must be checked in at least 60 minutes prior to the departure time. At LGA, meanwhile, the minimum check-in time for flying domestically with a checked bag is 45 minutes.

Even if you selected your seat when you purchased your flight and you’re not checking a bag, it’s wise to check in as early as possible. For starters, this ensures that as soon as you get to the airport, you can just make your way to security. It may also increase your chances of getting upgraded. Some airlines allow you to request upgrades at check in, and date and time of the upgrade request are often a consideration when it comes to determining who gets upgraded. If there’s only room for one more upgrade, and you submit your upgrade request two hours before another passenger with your same status puts in theirs, you may be more likely to get it.

It’s important to note that just because you check in online 24 hours prior to your flight, that doesn’t mean that you can rock up to the airport 30 minutes before your scheduled departure. “Delta recommends arriving at the airport two hours prior to domestic and three hours prior to international flights,” says the Delta spokesperson. To keep lines at the counter down, the airline also prefers that you check in via the Fly Delta app or at delta.com. Most airlines share this sentiment.

To make the process even more seamless, see if your airline offers an automatic check-in option. For example, Southwest allows passengers to add EarlyBird Check-In, starting around $15 each way, when they purchase their flights. If you get EarlyBird Check-In, which is complimentary in Southwest’s “Anytime” class fares, you’ll have peace of mind knowing that you’ll be automatically checked in 36 hours before departure. Passengers without this perk can’t check in until 24 hours prior to departure. The sooner you check in on Southwest, the sooner you can choose a seat and board the plane, which is helpful when it comes to getting precious overhead bin space. Singapore Airlines, meanwhile, has an auto check-in box under the “Manage Booking” tab that you can tick after you purchase your flight and up to 48 hours before departure. It doesn’t cost extra, and it ensures that you’ll be automatically checked in.

If you do have to check in at the airport at the last minute, don’t stress too much about the long lines at the check-in counters inside. Many airports now have self-serve kiosks where you can check yourself in, so look for those. Major airlines at major airports also have curbside check-in counters where you can check in and drop off any bags you want to check. These curbside counters usually have much shorter lines. It’s a convenient service that ranges from free to a few bucks, plus a recommended per-bag tip.