From physorg: The Best Way to Board a Plane.

"I remember waiting in line to scan my ticket inside the terminal, I believe it was at the Seattle airport," Steffen told PhysOrg.com. "I remember being quite disappointed when I saw how long the second line was — the one at the entrance to the airplane — and how slowly it moved. . . . That’s when I thought that there had to be a better way to get people onto the airplane than the one that was being employed. I didn’t have the time to work on it right then, so I brooded over it for almost 18 months. Last year, I decided that I either needed to solve the problem or stop thinking about it."

In his analysis, Steffen found that the worst method for boarding a plane is boarding from the front to the back, since passengers have to wait and step over each other to get to their seats. As he explains in a paper submitted to the Journal of Air Transport Management, conventional wisdom suggests that boarding in a manner opposite to the slowest method seems like it should be the fastest method. Quite unexpectedly, then, Steffen found that the common back-to-front boarding method is actually the second worst method possible, only slightly better than boarding front to back. (…)

Using a combination of a Monte Carlo optimization algorithm and intuition, Steffen determined an optimal boarding method, which could make boarding go 4 to 10 times faster than the worst method, depending on the size of the plane. In the optimal method, [continue]