American Airlines has a new tactic for shaming boarding line cutters: A loud beeper.

CNBC reports that the airline is rolling out a system that emits two loud beeps when a traveler tries to get on an airplane before their boarding group is called.

As of Wednesday, the new tech was in over 100 airports around the U.S. following tests at Albuquerque International Sunport, Ronald Reagan Washington National Airport, and Tucson International Airport.

CNBC notes that other airlines have experimented with less, well, audible ways to prevent gate crowding, which can interfere with the boarding process for flyers who pay a premium to get seated early. United, for example, texts customers when it’s time to board, provides a countdown-to-boarding clock via its iOS app, and has digital signs showing which boarding group has been called.