organising large groups into a single file line ordered perfectly. Steffen said this was likely the reason no airlines have adopted his method. Variations Due to criticisms of the stress and required organisation of the method, some have suggested other sub-optimal boarding methods that don't take such a toll on human imperfections. Steffen realised the impracticality of the logistics of his method, and so devised a modified method, where people boarded in the order of: Right side, odd-numbered rows Left side, odd-numbered rows Right side, even-numbered rows Left side, even-numbered rows This "Steffen Modified" method addresses the criticism of groups being split up, but is twice as slow as the optimal method. Another speedy boarding method suggested is the Southwest method, which consists of people being able to choose where they want to sit. While not as fast as Steffen, this method has been shown to have been faster than the standard back-to-front method in controlled experiments. References Planes