But increasingly, this most elemental of plane features is getting a makeover, with airlines slimming them down, eking out extra legroom, even turning them into beds to attract more fliers and stand out from their peers.

JetBlue's lie-flat seats will make their debut next year on non-stop flights between New York and Los Angeles, and New York and San Francisco.

United began featuring slimmer seats on its Airbus fleet in May, promising more legroom even as it squeezed on extra seats.

In September, Delta will begin receiving the first of dozens of Boeing jets with power outlets at seats throughout the plane.

"I would say that definitely it has become an increasingly important part of the travel experience," says Jami Counter, senior director of SeatGuru, a website that offers information and reviews of airline seats, services and amenities. "Obviously, you always needed a seat, but 15 years ago, an airline seat was an airline seat was an airline seat, at least in economy. There wasn't much differentiation."

Now, "what you've seen is a fairly rapid investment, focus on innovation," Counter continues. "You have seatback TVs. Power ports are becoming more ubiquitous, and you've gone to lighter-weight seats that allow airlines to put in additional rows of seats without impacting passenger comfort."

When JetBlue's lie-flat seats debut next year, the cross-country flights will also include suites that allow passengers to shut a door and recline in privacy. The airline is also enabling passengers to stay powered up throughout their time in the air, adding USB ports at all seats in its fleet next year.

"At JetBlue, we are always seeking new ways to enhance the travel experience," Kelly Roe, director of JetBlue's A321 Programs, said in an e-mail. "Seats are clearly an integral part of that experience. It's where a customer spends the most time with us."

New or improved seating is also a way for airlines to make more money, whether they're putting lie-flat seats in premium cabins, charging for extra legroom in coach, or squeezing in a few more seats to allow more passengers on board.

United Airlines began featuring new, slimmer seats on some of its Airbus jets in the spring, and will ultimately offer them on all 152 of its Airbus planes.

The economy-class seats, which are not as thick or wide as the traditional airline perches, offer passengers 1.2 more inches of space at knee level, and allow the airline to squeeze six additional seats on board. The slimmer seats also have head rests that move in multiple directions, a bottom cushion with extra padding and seat-back pockets that are higher than the standard pouch.

"It does provide us the ability to have more revenue," Martin Hand, United's senior vice president of customer experience, said of the slimmer design, allowing the airline to install additional seats. "The profits of this industry can be slim, so we felt this was a good item where we could improve the overall customer experience, improve the economics, and continue the investment we're doing" overall in the airline.

Counter says that the so-called "slim-line" seats, such as those being added by United, enable airlines to squeeze one or two more rows into a narrow body jet, and possibly as many as four additional rows in a wide-body plane. Those extra seats, Counter says, can be "the difference between several hundred dollars of profit, and not being profitable" on a given flight.

Counter also expects airlines to get more creative configuring cabins.

"Instead of forward-facing seats," he says, for instance, "some seats may be more angled to allow for more effective leg room without taking up more space in the cabin."

John Zazverskey, a regional sales director for a connectivity products manufacturer who travels 47 weeks of the year, says his in-flight perch is critical.

"Physical seat size is very key in choosing flights," says Zazverskey, who lives in Plymouth, Minn., and is part of USA TODAY's Road Warrior panel. He added that the actual seat and legroom outrank having a power outlet or big seat-back screen.

Keith Sorrels, another USA TODAY Road Warrior who is senior vice president of sales for a prepaid financial services company, living in Louisville, says he likes the extra legroom offering at Delta. "First class is always the best, especially the aircraft that have AC power ports and seat-back screens," he says. But "Delta's economy comfort is the next best thing to first with the extra legroom and bigger, more comfortable seating."

But some passengers feel U.S. airlines have a ways to go to catch up with their international peers when it comes to seating.

Road Warrior Rob Newman appreciates many of the recent innovations to the business-class seats he finds on international flights, saying they "are far superior to the first-class seats of the past." But he's more impressed with what he finds in the premium cabins on foreign carriers, like Emirates and Singapore Airlines, than what he sees on U.S. carriers.

"Too much of the U.S. (business) class seats are mediocre with a slight recline," Newman says. "Most coach is just OK, but again made better by seat-back televisions ... and a bit of extra legroom."

With most U.S. carriers having added lie-flat seats to their premium cabins for many long-distance flights, Counter of SeatGuru can see airlines shifting much of their focus to economy. And improving the seat offerings will be a key part of any upgrades.