Southwest Airlines passengers made their final boarding-time scrambles for seats on Monday as the carrier prepared to end the open-seating system that distinguished it from other airlines for more than a half‑century.

Starting Tuesday, customers on Southwest flights will have assigned seats and the option of paying more to get their preferred seat closer to the front of a plane or seats with extra legroom. The airline began selling tickets shaped by the new policy in July.

Here’s what travelers can expect as Southwest does away with another of its signature features and becomes more like other airlines:

Goodbye, A/B/C groups

Under the open-seat system, Southwest customers could check in starting exactly 24 hours before departure to secure places in boarding lines at departure gates.