American Airlines’ new pilot boarding program is a line cutter’s nightmare. The Fort Worth-based airline is testing a new technology that publicly shames passengers who try to skip the line.

When a passenger tries to board the plane ahead of the designated group, the new system makes a noise, alerting the gate agent that the flyer is trying to board the plane early. Those passengers are then told to join the line and wait their turn.

So far, the program is being used at Albuquerque International Sunport in New Mexico, Tucson International Airport in Arizona, and Ronald Reagan Washington National Airport in Virginia. The technology is currently in a trial phase, but in an emailed statement American Airlines said it was pleased with the results.

“The new technology is designed to ensure customers easily receive the benefits of priority boarding and helps improve the boarding experience by providing greater visibility into boarding progress for our team,” American Airlines said.

Airlines have long peddled the idea of ​​”priority boarding”—that earlier boarding is better. The benefit is offered to business and premium saver fliers and travelers with frequent flyer status or a co-branded credit card. either buy cheaper tickets or don’t fly an airline regularly to wait for boarding and can board earlier eg gate agents can allow them to tag along with their previous boarding partner. Families traveling with younger children, travelers requiring additional assistance and service members are entitled to early boarding.

But what is the motivation for anyone else trying to board earlier than when the group named on the boarding pass is called?

“Travelers who sneak in early probably do it for one thing: coveted overhead bin space,” says Katy Nastro, travel expert at Going.coma flight deals app. “With limited headroom, getting on the plane earlier means you’re more likely to keep your carry-on than having to check in at the gate and pick up your bags. Some of us don’t mind checking at the gate, but for others, it defeats the whole purpose of bringing a carry-on to begin with.”

And if passengers have to wait for their baggage to be brought onto the flight deck after the flight (as opposed to checking it at their final destination) and have a tight connection, carrying their carry-on in the overhead compartment could be the difference between make the flight or not.

However, studies have shown that passengers crowding the gate – referred to as “gate lice” – and lining up too early cause congestion around the gate and on the jet bridge, which in turn leads to general confusion, slower boarding overall and, sometimes, departure delays.

However, Gary Leff, a travel expert and founder of the blog Wing viewsaid that while they’d rather wait until boarding, there’s a reason many travelers are anxious to take their seats.

“Why spend more time in an airplane seat than you have to?” says Leff. “However, I think people try to board earlier – and earlier than they should – because they feel more confident once they’re firmly secured in their seat. They did everything they could to make sure their trip went smoothly. Everything in their control, from getting to the airport to going through security and getting on the plane is ready.”