Boarding an aircraft looks like a logistics problem. It is really a queueing problem, and the math says almost everything airlines actually do is wrong. The enemy is interference, and two kinds dominate: • Aisle interference: a passenger stops to stow luggage and blocks everyone behind them • Seat interference: an aisle or middle passenger has to stand and clear out so a window passenger can sit down Both serialize the process. One useful action happens at a time, and the aisle, your highest-throughput resource, sits mostly idle. Back-to-front feels orderly, so airlines love it. But filling the rear rows first packs passengers into the same zone, where they queue to stow bags one at a time. In simulation it performs about as badly as front-to-back, near the theoretical worst case. Random boarding beats it. With no structure, passengers spread along the cabin, so several people stow luggage at once. Chaos parallelizes the aisle better than a tidy back-to-front block does. The St...