Airplanes, of course, are typically heavier in the back. The back is where the engines are located. If commercial airlines boarded passengers from the back to the front, it will add more weight to this area. All of this weight could cause the back of the airplane to sink down while potentially sustaining damage.

While loading a plane from the back to the front seems more logical to prevent aisle congestion, most airlines avoid it for two main reasons: stability and profitability. From a technical "Weight and Balance" perspective, loading the back of a plane first can make the aircraft "tail-heavy," which in extreme cases could cause the nose to tip up while the plane is parked at the gate. Loading the front or middle sections first helps keep the center of gravity stable. However, the bigger driver in 2026 is loyalty and revenue. Airlines prioritize "Zone 1" boarding for First Class, Business Class, and Elite status members who pay a premium. These passengers want to board early to ensure overhead bin space for their carry-ons. Efficiency studies (like the "Steffen Method") show that random boarding or "outside-in" (window, then middle, then aisle) is actually the fastest way to board, but airlines find these methods difficult to manage at the gate compared to the traditional, tiered "front-to-back" or "zone" systems.