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Airplanes Making Up for Lost Time

Q: When a flight departs late, why can’t the pilots simply pour on the coals to make up lost time? It’s not like the air police are going to give you a speeding ticket, right?

Well, no, but it’s a lot more complicated than that. Airplanes usually cruise fairly close to their maximum speed, measured as “Mach number” (the percentage of the speed of sound, which itself varies). However, flights normally follow one another along routings that aren’t unlike highways in the sky, needing to be sequenced and spaced apart.

It is easier to make up lost time over long, straight routings, such as across the country or across the ocean, than while flying along crowded corridors with lots of twists and turns, but even then the savings is usually slight as there’s not a whole lot of difference between, say, .84 Mach and .86 Mach. Also, “pouring on the coals” will affect fuel burn, which is sometimes pre-planned under fairly tight constraints.

While flying at lower altitudes, by the way, there are various speed limits that pilots must observe.

This Q&A is part of a collection that originally appeared on 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 Patrick has traveled to more than 55 countries and always asks for a window seat. He lives near Boston.