You'll Always Board a Plane from the Left. Here's Why.

Have you noticed that when boarding a commercial airplane, whether from a jet bridge or steps leading up from the tarmac, you always enter from the left side? Ever wonder why?

While this practice is universally adhered to, the reasoning behind it is not widely known. It stems from a mix of historical traditions and operational efficiency.

“This practice in aviation dates back to maritime traditions,” explains Michael Oakley, managing editor of The Aviation Historian, a quarterly journal focusing on aviation history. “Much of aviation terminology comes from nautical language (like rudder, cockpit, cabin, and knots), and similarly, aviation practices are influenced by sailing traditions. Just as boats have a port side—the side closest to the dock—aircraft follow suit. Thus, it makes sense to board from the port (or left) side.”

However, in the early days of commercial aviation, which side passengers boarded didn’t hold much importance, Oakley notes, as travelers would simply walk up steps onto the tarmac.

“In the 1930s, the Boeing 247—the first modern airliner—featured a passenger door on the right, following the custom of United Airlines at the time,” explained Bob van der Linden, a supervisory curator at the National Air and Space Museum in Washington, D.C. “When United acquired the remarkable Douglas DC-3 in the mid-1940s, they opted for a right-hand door, while most other operators chose a left-hand door. As the industry expanded and airports grew busier, the left-hand door became the standard for streamlining operations.”

Matthew Burchette, senior curator at the Museum of Flight in Tukwila, Washington, noted that standardization became increasingly essential in the 1950s with the introduction of star-shaped or “pier finger” terminals in the U.S. and Europe. Airports like Chicago’s O’Hare, Amsterdam’s Schiphol, and London’s Gatwick feature central areas from which passengers walk out to the terminal fingers to board their flights.

“Now, passengers could directly board from these fingers into the planes. In the 1960s, the design adapted to include Jetways—the enclosed walkways we recognize today,” Burchette said. “With pilots seated on the left, airports began to be designed with left-side gates, allowing pilots to better gauge distances while taxiing to the gate.”

Oakley supported this reasoning: “As more advanced airports emerged, with passengers using Jetways to board directly from the terminal, it simplified ground operations if every aircraft followed the same boarding direction.”

Boarding from the left also provides an advantage: “It enables ground crews to carry out their work without interference from passengers or gate equipment,” Burchette remarked. With a dedicated access area, the crew can perform their tasks more efficiently and swiftly, contributing to a smoother travel experience for everyone involved.