Boarding-pass codes reveal how seating and security decisions are driven by travel-tech codes

Air travelers may not notice the small numbers printed on the bottom of boarding passes, but those codes help airlines manage seating, boarding and security processing. In recent reporting, industry watchers highlighted several codes including the sequence number, or SEQ, that can influence where a passenger sits. The notes describe how some airlines allocate seats in the order travelers check in, meaning late arrivals could end up in less desirable seats regardless of flight length or fare class. The information comes from industry outlets such as Simple Flying and a Daily Mail summary of their reporting.

SEQ indicates the boarding order and can be shown as a code like SEQ08, signaling the eighth person to have checked in. Depending on the carrier, the sequence number may determine whether a seat is assigned during check-in or at the gate, and it can affect when a passenger is able to board a full flight. In some cases, last-minute check-ins on a crowded flight may lead to seating changes or even rerouting to another aircraft if the original flight becomes oversold.

Another common code on boarding passes is the group number, often displayed as Group 1 or Group 2. Airlines use these groups to organize boarding, usually prioritizing travelers such as families who need to board together, passengers with disabilities, or those in higher fare classes. The presence of a group designation can help gate agents call boarding zones in a way that aligns with each airline’s policies and the flight’s capacity.

SSSS stands for Secondary Security Screening Selection. When this tag appears on a boarding pass, it means the passenger will undergo an enhanced security screening conducted by the Transportation Security Administration (TSA) in the United States. The extra screening is designed to tighten security and can add meaningful time to the journey, potentially contributing to delays if lines are long or if additional checks are required.

Airlines also sometimes overbook planes, a common practice in which more tickets are sold than there are seats. When everyone shows up, those who checked in last and cannot be accommodated may be moved to another flight or rebooked into a later departure. This practice underscores how boarding codes intersect with operational decisions and passenger outcomes, particularly on busy routes or peak travel days.

The booking reference, or reservation number, is another key element that appears on boarding passes. The Passenger Name Record (PNR) is a six-digit alphanumeric code that uniquely identifies a passenger in the airline’s system. The PNR links to a detailed travel itinerary, including flight details, meal preferences and frequent-flyer status. The PNR helps airlines manage complex reservations and allows agents to retrieve a passenger’s travel history and preferences even if there are multiple travelers with similar names.

Taken together, these codes illustrate how airlines blend boarding logistics with data-driven processes to manage capacity and optimize the travel experience. For travelers, the codes serve as a reminder to review the boarding pass carefully: early check-in can influence seating and early gate calls, while awareness of SSSS flags can prepare passengers for potential security delays.

Experts note that the use of such codes reflects a broader trend of technology-enabled automation in travel. As airlines increasingly rely on standardized data fields to coordinate seating, boarding, and screening, the line between human-assisted service and algorithmic decision-making continues to blur. From a technology and AI perspective, the codes represent a practical layer where data, process design and operational efficiency intersect with passenger experience, privacy considerations and the occasional impact on travel timing. Travelers are advised to stay informed about their airline’s boarding policies, check in as early as possible, and monitor any notices at the gate to understand how these codes may affect their own journey.