Numbers Along the Edge of the Runway

Q: I noticed a successive arrangement of signs along the edge of the runway. Each sign featured a single digit, and these went in order: 9,8,7,6, and so on. Is this some kind of distance marking?

Yes, these signs indicate the distance remaining, measured in thousands of feet. If you’re departing on a typical 10,000 foot strip, expect to see a 4 or 5 zipping by as you leave the payment. This depends, however. I remember a takeoff once in a 727 from the airport in Cuzco, Peru, high in the Andes. The “2” sign went past my window in a blur while the tires were still firmly on the ground. But don’t fret, as takeoff distances are calculated prior to every departure to ensure adequate distance not only for taking off, but for stopping should something occur.

Runway striping also can be used to measure distance, but this usually isn’t visible from the cabin. The various signs and markings strewn about the airport can seem baffling to a passenger. This particular section of the Aeronautical Information Manual features 27 pages of diagrams and explanations.

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This Q&A is part of a collection that originally appeared on Salon.com. Patrick Smith, 38, is an erstwhile airline pilot, retired punk rocker and air travel columnist. His book, Ask the Pilot (Riverhead) was voted “Best Travel Book of 2004” by Amazon.com. Patrick has traveled to more than 55 countries and always asks for a window seat. He lives near Boston.