The One Crucial Flight Move Travelers Should Never Skip (Even If They're Checking A Bag)

You've booked your flight, made a packing list, secured reservations for all the museums and restaurants you want to visit, and ensured everything is ready for your vacation. However, there may be a move you're skipping that could negatively affect your trip: waiting to check in for your flight. While there are some variations here and there, you're generally allowed to check in for your flight online 24 hours before departure time. That's true even if you're checking a bag. If you wait until you get to the airport, you could be out of luck in several different ways. 

First, while some ticket classes let you pick a seat when you purchase your ticket, others assign one at check-in. If you don't check in early online, you may end up fighting for armrest space in the middle seat — and if you're on a long flight, that can make things really uncomfortable. In addition, if the check-in line at the airport is long, you could end up missing your flight, as, generally, domestic flights open in-person check in two to three hours before departure, with international check-in generally opening three to four hours in advance. There are also bag drop cut-off times, and if you miss yours, your bags may be left behind. There are kiosks at the airport to check in and print your boarding pass at, of course, but those can have lines as well. Instead, use them to print your boarding pass when you arrive, after you've checked in online. However, those aren't the only reasons that early online check-in is essential.

Perhaps the biggest reason to check in online as early as you can is that it can ensure you're able to stay on the flight. You may know that airlines are allowed by the U.S. Department of Transportation to oversell their flights to compensate for no-shows. However, if the flight is overbooked and everyone shows up, there is an issue. Generally, the airline will ask people to volunteer to give up their seat to be rebooked on another flight, sometimes with perks like financial compensation. However, if not enough fliers volunteer, the carrier may have to bump people off the flight. Usually those with high frequent flier status and those who paid more for tickets are least likely to end up on the chopping block, and those who checked in at the last minute may be the first to be removed.

In fact, there is something called a sequence number on your boarding pass that is more important that people realize. It's a three-number sequence that appears after the letters "SEQ," and it shows the order that people checked in. You don't have to be like some passengers who try to get SEQ 001 by keeping their fingers hovering over the check-in button online, but the earlier your check-in is confirmed, the less likely you are to be bumped. In addition, even if you've checked in online, make sure you get to the airport in plenty of time, which is generally recommended as two hours before a domestic flight and three hours before an international flight. That way, things like a long security line, any issues with your boarding pass, or other little snafus won't derail your vacation before you even leave.