H051
Is boarding a plane back-to-front the fastest way?
Filling the back rows first sounds like it keeps people out of each other's way. In practice it puts everyone in the same few rows at the same time.
Time to seat 72 passengers in a mock 757 cabin
Each method tested with the same passengers and their real carry-on bags
Sending everyone to the same part of the plane makes them wait for each other. When boarding goes back-to-front, everyone in the aisle is heading for the same few rows, so each person stowing a bag blocks the whole line. In random order, people stow bags in many rows at once. In a 2011 test with 72 passengers, random boarding beat back-to-front by almost a minute and a half.
Orderly-looking plans can create one narrow bottleneck that everyone has to pass through. The fastest systems often spread the work out, even if they look messier.
Try it somewhere else
A school lets students into the cafeteria one grade at a time, and every student in a grade heads to the same serving line.
Would letting everyone in at once, spread across all the lines, be slower or faster?
Why the fastest method isn't used
The Steffen method seats passengers in alternating rows, window seats first, so people stowing bags are two rows apart and never block each other. It needs passengers to line up in a precise order, which is hard with families, late arrivals, and boarding groups that airlines sell as perks. Many airlines now use window-middle-aisle or simply let groups board without assigned order within them.
Related exhibits
Sources: Jason H. Steffen and Jon Hotchkiss, "Experimental test of airplane boarding methods," Journal of Air Transport Management, 2012 (72 passengers, mock Boeing 757 cabin; official boarding times).