Q. Is it just my imagination, or have airplane seats become “thinner” than they used to be? I’m old enough to remember flying on Lockheed Constellations when I was a kid, and I seem to recall that the seats were as comfortable as a luxury automobile seat. Now they’re hard as marble.

A. No, it’s not your imagination. Airplane seats are getting thinner. It’s all about saving fuel (lighter, thinner seats weigh less) and allowing the airlines to squeeze more seats onto their planes. Because the seat backs are thinner (and, as you’ve no doubt noticed, have less cushioning) they provide more knee space (if not more legroom). So they give the illusion of providing just as much space as thicker seats that used to be spaced farther apart. For domestic U.S. travel, JetBlue still offers the most legroom in economy class; Spirit Airlines offers the least.