Ben Mutzabaugh

USA TODAY

American has formally introduced its long-expected Basic Economy fare class, saying the fare type will first go up for sale this February in 10 “select markets.”

With that, all three of the USA’s biggest airlines have now introduced their own versions of a basic economy fare. Like at United, fliers buying American’s Basic Economy fare will only be able to bring onboard carry-ons small enough to fit under the seat in front of them. Delta, the first to introduce a version of basic economy, does not restrict carry-ons.

For American, carry-ons that must be stowed in overhead bins are not allowed -- though elite-level frequent-fliers and holders of certain American Airlines-branded credit cards will be exempted.

American's Basic Economy fares also will not allow changes -- not even for a fee -- and will make fliers among the last to board the plane. The fares will earn frequent-flier miles, but elite status will be earned more slowly for those buying Basic Economy. Seats will be assigned at check-in or can be selected within 48 hours of departure for a fee.

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The new Basic Economy fares now in place at the USA's three biggest airlines (American, Delta and United) have been developed as a weapon to battle a new breed of budget carriers rapidly expanding at major hubs. Those airlines – notably “ultra low-cost carriers” such as Spirit, Frontier and Allegiant – are known for charging rock-bottom base fares but adding fees for everything from seat assignments to water. They also charge a fee for using their overhead bin space. But, even with their fee-heavy structures, those budget outfits often compare favorably to major "full-service" airlines in online fare searches.

“We have to compete aggressively on price against carriers like that,” American CEO Doug Parker said in October, when he acknowledged such fares were in the works. “When they add flights to our hubs, we actually have a competitive advantage because we have so much connecting activity."

American President Robert Isom picked up on that theme in the company’s formal Basic Economy announcement on Wednesday.

"American Airlines now has something to offer every customer, from those who want simple, low-price travel to those who want an ultra-premium experience via First Class," Isom said in a statement. "Importantly, this new fare product also gives American the ability to compete more effectively with the growing number of ultra low-cost carriers."

American said its Basic Economy fares would gradually expand to more markets but said that they would not be rolled to all of the flights in its system.

American also outlined what other restrictions would – and would not – come for customers buying its Basic Economy fares. In its statement, American offered the following “what to expect” guidance for fliers buying its Basic Economy fares. Scroll down to see the details in American's own words:

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In-flight experience: The same in-flight experience that all Main Cabin customers receive today, including free entertainment options, soft drinks, and snacks, and the same seats.

Seat assignments: Made automatically and only when customers check in. Paid seat assignments can be purchased 48 hours before the flight.

Upgrades: Not permitted, regardless of elite status level.

Bags: One personal carry-on item that fits under the seat (such as a purse or small backpack) is allowed. No overhead bin luggage may be brought on board. Larger carry-ons such as a rollerboard bag must be checked at the ticket counter for the applicable checked-baggage charge. Basic Economy customers who bring more than an under-seat personal item to the gate will incur regular checked baggage charges plus a $25 gate service charge per bag.

Elite customers and eligible AAdvantage credit cardmembers will be allowed to bring one personal item, one rollerboard, and they maintain their current free checked bag allowance.

Boarding: Basic Economy customers will comprise the last boarding group and will be seated in the Main Cabin. Elite customers and eligible AAdvantage credit cardmembers will continue to receive Priority or preferred boarding even when purchasing this fare.

Tickets: Non-refundable, non-changeable. Use it or lose it. No same-day flight change or same-day standby.

AAdvantage: Full AAdvantage miles and Elite Qualifying Dollars may be earned when purchasing these fares; however, only one-half Elite Qualifying Mile will be earned per mile flown, and one-half Elite Qualifying Segment per segment flown.

Now flying on American: Real international-style premium economy seats