The half-empty United flight at the center of a corruption probe

In the airline business, filling seats is everything.

Whether it’s packed or empty, airlines have to pay for fuel, flight crews and everything else it takes to get a plane off the ground. So to boost profits, airlines try to get as many people on board as they can.

Efforts to fill up planes have spawned seat designs that look like torture devices, a federal investigation into potential collusion and a constant peeve of travelers: no leg room.

In fact, the percentage of seats that fly empty has been dwindling for more than a decade, federal data show — that is, it’s been getting harder and harder to luck out and get a row to yourself.

But if you flew between Newark and Columbia, S.C., back when United offered that route, you had a pretty good chance of being able to spread out.

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