A simple mistake can lead to big problems at the airport. For example, a slip-up like incorrectly entering the wrong birthdate on your ticket can get you kicked out of the TSA line and sent hoofing it back to the check-in counter. Recently, there have been reports of another straightforward task resulting in costly consequences when it goes wrong. Here’s what you need to know.
What happens if a boarding pass doesn’t scan correctly

Whether they use paper or digital boarding passes, every airline passenger has one. When it’s time to board, this pass needs to be scanned into the airline’s system.
When your pass scans correctly, you’ll probably hear a reassuring tone, see a green light, or both. When it doesn’t, you’re likely to hear an alarming buzz, a red light, or both. At this point, the gate agent should step in and ask you to re-scan your pass. Unfortunately, this doesn’t always happen, and passengers are paying the price for the oversight.
What can happen after a mis-scan

On Reddit, flyers have been posting stories about boarding agents waving them through after a mis-scan, only to discover later that the airline’s system didn’t recognize they were on board. That single failure can unravel an entire itinerary.
In the United Airlines Reddit community, a traveler described flying with their family of five from Newark to Orlando. Everything about the boarding process felt normal. They scanned their passes, walked down the jet bridge, took their seats, and completed the flight without realizing anything had gone wrong.
The problem surfaced seven days later when they opened their reservation and found their return trip was missing. United’s system flagged all five passengers as no-shows on the first segment, triggering an automatic cancellation of the rest of the itinerary. To make things worse, the airline refused to reimburse them for flight costs or accommodations while it was sorted out.
The family provided proof of a bag checked at the gate and a receipt from the immigration kiosk, but they were told they were out of luck. In the end, each family member received a $100 voucher for future travel and a meal voucher.
The traveler completed their post by stating, “ I fail to understand how United has no record of their passengers boarding flights. Unbelievable.”
Forced to buy an expensive ticket to get home

United Airlines passengers aren’t the only travelers facing this issue. A similar event was reported in the American Airlines community.. In a post, a traveler reported boarding a flight after several delays. Shortly after arriving at his destination, he received an email notifying him that his return trip had been canceled. Naturally, he called customer service.
The customer service agent insisted the man hadn’t boarded the flight and said he’d need to book a new ticket to get home. The traveler said, “The original flight is apparently booked, and the earlier flight they can get me on costs a lot more than the original round-trip ticket cost.”
Fortunately, his father had enough airline miles to buy a new ticket for the return trip. Otherwise, he might have been stranded.
Stuck at the airport

More recently, a member of the United Airlines community went to the airport for a return flight home from LAX, only to find their ticket had been canceled. The airline claimed they canceled the ticket because he “never boarded the first flight in the round-trip itinerary.” The traveler says this isn’t the case.
According to the post, not only did the traveler scan their boarding pass, but they gate checked their bag “because of no overhead space.” In the end, United refused to help, and they were on standby with another airline. “Paid out of pocket for this,” said the post.
Based on the evidence, it appears that although the traveler scanned their boarding pass, it didn’t get entered into the system. This is why it’s essential you wait for the green light and accepted tone before you walk down the runway.
The bottom line

Boarding passes don’t always scan correctly. If the scanner makes an unexpected sound or the light flashes anything other than green, try again. If the issue persists, ask the agent to confirm that the system shows you as boarded. A few seconds of confirmation at the gate can prevent a long and expensive detour later.

