Many passenger aircraft have two doors, but typically are boarded using only one. Southwest Airlines is experimenting with a new boarding system using both doors that is facilitated by its system of not assigning seats to passengers.

USA Today reports that the airline is testing out the system at several airports, including Sacramento International Airport. A reporter on one flight noted that she was in the airport terminal four minutes after her plane reached her gate despite having a seat in the rear of the aircraft; the quick debarkation was aided by her use of the rear door.

Southwest officials said that “turn times” — the amount of time it takes to debark passengers at the gate, load new passengers, and depart — have been quicker at airports where the airline can use both aircraft doors to load and unload passengers.

Passengers using the front door of Southwest’s 737 jets typically debark onto a jetbridge, whereas those who exit from the rear use stairs and have a brief walk across the airport tarmac to the terminal.

Gate attendants offer travellers the option of boarding from the front or rear; some choose the latter in hopes of getting a preferred seat or bin space for luggage. Passengers are advised, however, not to use the rear door and try to rush to seats in the front of the plane.