Final answer:
The code S1 on a boarding pass typically signifies a seat upgrade. This means the passenger has been moved to a higher class of service. Codes can vary by airline, so direct confirmation from the carrier is advised.
Step-by-step explanation:
The code S1 on a boarding pass typically stands for seat upgrade. This code is used to indicate that the passenger has been upgraded to a higher class of service, which might be due to status with the airline's frequent flyer program, the purchase of an upgrade, or other factors. However, it's important to note that boarding pass codes can vary by airline, so it's always best to check with the issuing carrier for the exact meaning.
Being marked with an S1 does not necessarily mean seating in the middle of the aircraft, speedy boarding, or that special assistance is required. Instead, it most commonly refers to a person being given a better seat than originally assigned. For example, moving from economy to business or first class, or to an economy plus seat with more legroom.