Oh, the things passengers do to avoid the worst seats on the plane.

They beg. They negotiate. They even lie.

If you’re flying somewhere this summer and aren’t willing to pay extra for a preferred seat in economy class, chances are better than ever that you’ll end up in the dreaded middle seat or relegated to the back, engulfed in engine noise.

Why? It all comes down to money. Airlines want more of yours, and they think you’re willing to fork it over in exchange for (relatively) desirable seating.

Several years ago, discount airlines cleverly separated confirmed seat reservations from tickets in an effort to lower their fares – or so they claimed. For the most part, prices didn’t change significantly; airlines just added a new fee. In 2012, Delta Air Lines began offering a “basic” economy-class fare that doesn’t allow you to reserve a seat in advance – almost guaranteeing a middle-seat sentence – and its competitors are rushing to offer a similar product.

More than half of air travelers say they’re annoyed by uncomfortable airline seats, according to Qualtrics’s latest Airline Pain Index. Yet charging passengers to avoid pain is immensely profitable. Airlines made almost $11 billion in a la carte fees last year, which includes seat-reservation charges – a 24 percent increase over 2014.

But it turns out there are ways of avoiding the worst airline seats. Some practical, some ethical, some borderline.

“Book well in advance,” says Mark Beales, a retired mortgage banker from Mill Creek, Washington. “And only with an airline allowing seat selection at the time of booking, if possible.” (With many airlines – this is particularly true of international airlines – it’s still first-come, first-served.) A frequent traveler, Beales has used the strategy often.

A free app called Seateroo, which calls itself an online market for airline seat swaps, lets you trade places with another customer – for a price. The app charges a 15 percent service fee; the minimum bid is $5.

James Goodnow, a lawyer and frequent air traveler from Phoenix, prefers to negotiate. He advises appealing to fellow passengers’ nobler natures. “If, for example, you’d like to sit closer to your kids, kindly ask the person in your target seat and explain your predicament,” he says. If that fails, you can always pull out your wallet and offer to buy your seatmate a drink.

Laura Marzola, a former flight attendant based in Charlotte says pressuring fellow travelers or telling tall tales often is unnecessary. “It’s been my experience that most people – especially solo travelers and those traveling without children – are pretty flexible about seating,” she says. “If you ask nicely, and with a good reason, like sitting next to a small child or someone needing special assistance, or requesting extra leg room because of a health condition, most passengers are usually willing to switch seats with you.”

Don Halbert, the chief executive of a tour operator that specializes in vacations to Costa Rica, offers this piece of contrarian advice: Book the worst possible seat. In the worst part of the plane – the back. Because people will do anything to avoid the entire area.

“Typically no one will want the solo middle seat in the back of the plane,” he says. “This leaves you with an entire seat . . . as opposed to paying for extra seating and getting a few inches.”

Chula Ranasinghe, a systems engineer from Davis, California, says understanding the psychology of substandard seat avoidance helps him create more space on a plane for his family.

When he travels with his wife and daughter, he requests an aisle, a window and a second aisle seat. Unless it’s a full flight, the middle seat will be the last one taken. “No one wants it,” Ranasinghe says. If someone shows up, they offer to switch, giving the person the option of sitting in an aisle seat. But in the best-case scenario, there will be extra space, because the middle seat is empty.

None of these strategies should be necessary, of course. Every seat on the plane should come with a minimum amount of legroom and space, and passengers shouldn’t have to beg, borrow or steal the slightly less painful seats from their fellow passengers.

And that’s something to remember as the summer travel season gets underway. Airlines will try to sell you back a little of the comfort that should have been yours to begin with. You can pay for it – but you don’t have to.

Special To The Washington Post · Christopher Elliott