This tiny detail on your boarding pass might determine whether your dream trip takes off or never gets off the ground
If you’ve ever taken the time to study a printed boarding pass—I mean really study it—you’ll notice that there’s a surprising amount of information packed on that tiny slip of paper. As I write this, I’m looking at one from a recent flight to Rome, and it lists all the usual suspects (flight time, flight operator and departure gate), along with other details not necessarily meant for me: My documents are okay, I requested a special meal, my TSA PreCheck is active and I checked a bag. There’s also a barcode and a string of letters and numbers that might as well be gibberish.
But then there are the codes that could cause some panic—an unwelcome development when all you want to do is board your flight and jet off to your destination. Some are better known, like the dreaded “SSSS,” which triggers extra security screening (a nightmare for someone like me whose more-often-than-not overstuffed carry-on barely zips). Others are more obscure.
One of them is a set of three little letters that many travelers overlook, and if they do notice them, they don’t understand why they matter. But in rare, worst-case scenarios, they can create major headaches for passengers who assumed they were getting on their flight. Coming up, Eric Napoli, chief legal officer at AirHelp, the world’s largest organization dedicated to air-passenger rights, explains what this trio of letters means, when to worry about them and what to do if they threaten to derail your trip—before it’s even started.
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What are the three letters on your boarding pass that could cause a problem?
It’s the code “SEQ,” which on your boarding pass stands for sequence number, and the three-letter code will be followed by a number. “This number indicates the order in which the boarding pass was issued,” Napoli says.
A lower SEQ number, for example, means you’ve checked in earlier than someone with a higher one. Most of the time, the SEQ doesn’t really matter, but in rare cases, it can. If a plane is oversold and there aren’t enough passengers willing to voluntarily give up their seats, check-in order might come into play when the airline decides who gets bumped. But it’s not the only thing.
“Other factors airlines may consider include elite status, fare class, full-fare passengers, airline crew or priority passengers,” Napoli adds. And there are some instances when the SEQ could actually work in a traveler’s favor. Gate agents sometimes may need to use the number to troubleshoot uncommon check-in errors or disputes, like duplicate boarding passes.
How many tickets generally get this designation?
All of them. “SEQ always appears on passengers’ boarding passes, regardless of peak/off-peak travel timing or if the flight is full or oversold,” Napoli says of the fairly standardized code that’s used across major global carriers. He adds that the SEQ is not linked to busy travel periods, like Christmas and New Year’s, and it “does not indicate a passenger’s status, boarding group, upgrade, frequent-flyer status or position if on standby for a flight.”
Is there anything you can do to lessen the chances of getting bumped?
Yes. “If trying to avoid a higher SEQ, the best tactic is to check in as early as possible,” Napoli says. (Most airlines open check-in 24 hours before a flight’s departure.)
Airlines use a complex mix of factors when deciding exactly who might get involuntarily bumped—also called “denied boarding”—from an oversold flight, so it’s always a smart idea to better your odds whenever you can.
“Overbooking flights is very common, and most major airlines regularly overbook their flights as they anticipate a certain number of no-shows each flight” due to factors such as missed connections and late cancellations, Napoli says. “Some estimates put the number of no-show passengers between 5% and 15%.”
What’s the best way to check in?
A carrier’s app or website is the quickest and most convenient way to check in, and it’s always a good idea to do it well in advance. If you want or need to wait until you’re at the airport, it’s important to remember that check-in cutoff times vary by airline and whether your trip is domestic or international.
Delta, for instance, closes domestic check-in 30 minutes before departure for travelers with carry-ons only, and 45 minutes for those who will be checking bags. If you’re traveling internationally, they recommend travelers check in 60 minutes before departure, regardless of whether they check a bag.
What happens if you are bumped from a flight?
Passengers who are involuntarily bumped are entitled to be rebooked for free on the next available flight, and those who qualify may be entitled to compensation, alternate flights or refunds and sometimes meals and hotel stays. “These factors will depend on the flight and where a passenger is traveling to/from and what airline,” Napoli says.
For domestic flights, compensation applies only when a passenger is denied boarding because the airline oversold the flight. For international travelers departing from the United States, oversold-flight compensation can be much higher—as much as $2,150, according to AirHelp.
If you’re bumped, keep your boarding pass and booking documents. Ask the airline why you were denied boarding, then request to be re-booked or refunded and file a compensation claim, if you’re eligible. “To file a claim, it will be important to have all the paperwork and details to make a strong case,” Napoli advises.
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Reader’s Digest has published hundreds of travel stories that help readers explore the world safely, easily and affordably. We regularly cover topics such as the best places to visit (and the best times to visit them), tips and tricks to zoom through airport security, flight-attendant secrets, hotel-room hacks and more. We’re committed to producing high-quality content by writers with expertise and experience in their field in consultation with relevant, qualified experts. We rely on reputable primary sources, including government and professional organizations and academic institutions as well as our writers’ personal experiences where appropriate. We verify all facts and data, back them with credible sourcing, and revisit them over time to ensure they remain accurate and up to date. Read more about our team, our contributors and our editorial policies.
Sources:
- Eric Napoli, chief legal officer at AirHelp; email interview, December 2025
- U.S. Department of Transportation: “Bumping & Oversales”
- Delta: “Check-In Times at U.S. Airports”
