[Read: America's Meanest Airlines: 2013.]
According to Lopinto, most window or aisle seats now have a seat assigned fee attached that can range from $20 to $100 depending on the airline and length of the flight. For passengers who don't want to find themselves wedged into a middle seat on a flight, ExpertFlyer offers free seat alerts. "We'll let you know if a better window or aisle seat comes available that you don't have to pay for," Lopinto says.
In most cases, passengers who don't pay for a seat assignment simply get assigned a seat at the airport once they check in. But in cases when a flight is oversold, passengers without a seat assignment may get involuntarily bumped.
Extra space. Several airlines now promote the availability of roomier seats for passengers who want to pay for one. On Air New Zealand, for instance, the Economy Skycouch is available on some long-haul flights and gives passengers the option to book a row of three seats to turn into a bed or use to curl up with children or a significant other.
Sometimes extra space and other perks like priority boarding are bundled together for one fee. For example, American Airlines offers Main Cabin Extra, which includes priority boarding and up to 6 inches of extra legroom. Passengers who pay for Even More Space seats on JetBlue get at least 8 inches of legroom, early boarding and early access to overhead bin space.
"Usually during the booking process, if you're a non-status member, you often see an offer to pay X dollars for priority lines, priority check-in and priority boarding," Lile says. Even if you don't have elite status with an airline, Lile adds that you can "simply buy your way in."