Southwest Airlines' CEO Gary Kelly spoke with CNBC's "Squawk Box" Thursday morning to discuss his company's 4th quarter earnings, and slipped in that while the company has no plans to add bag fees in 2013, he "never says never" on that policy. "The customers will tell us whether they would prefer to have extra fees or whether they would prefer to have everything bundled," he said.

For those keeping track, Southwest's earnings fell by nearly half on higher spending but its revenues rose slightly, according to the Associated Press.

Earlier this week, the airline announced that it would offer a $40 charge for passengers who wanted to be among the first 15 to board a flight. In December, the airline quietly announced that it would start charging for no-shows who purchased the cheapest "Wanna Get Away" fares sometime in 2013.

Southwest has regularly been considered amongst Americans' favorite airlines. (It came in third in SkyTrax's best low-cost American carrier survey in the summer of 2012.) Yet Kelly alluded to the ferocity of the competition in the airline landscape in his CNBC interview.

Unlike Southwest, its subsidiary AirTran announced new bag fees last December, including a $25 fee for the first checked bag (up from $20) and $35 for the second (up from $25,) the Associated Press reported. Thanks to AirTran's fees, Southwest collected $104.3 million in bag fees last year.

To listen to the interview, click over to CNBC.

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  • Blanket Fee

    Back in 2010, American Airlines <a href="http://www.huffingtonpost.com/2010/02/08/american-airlines-to-char_n_454109.html" target="_hplink">started charging $8 for blankets</a>.

  • Ryanair Boarding Pass Fees

    Songstress Lily Allen took to twitter to express anger over<a href="http://news.travel.aol.com/2011/06/06/lily-allen-twitter-ryanair-boarding-pass/" target="_hplink"> Ryanair's policy of charging passengers to print out their boarding passes</a>.

  • Spirit's Online Booking Fee

    In November 2011, Spirit Airlines <a href="http://www.huffingtonpost.com/2011/11/14/spirit-airlines-raises-on_0_n_1093430.html" target="_hplink">raised its domestic "passenger usage fee" (aka online booking fee) from $8.99 to $16.99</a> each way.

  • Fuel Fees

    Southwest Airlines <a href="http://www.huffingtonpost.com/2012/03/26/southwest-airlines-fees-fuel-costs_n_1381008.html" target="_hplink">raised its ticket prices by $4 to $10 to offset the high cost of jet fuel</a> in March 2012. Its subsidiary AirTran, plus United Airlines, Delta Air Lines, American Airlines, US Airways, Frontier Airlines and Virgin America followed suit.

  • Ryanair Emergency Row Fee

    Ryanair found itself under investigation after <a href="http://www.huffingtonpost.com/2012/03/20/ryanair-in-hot-water-over_n_1366497.html" target="_hplink">instituting a 10 pound fee to sit in the emergency row</a>.

  • Allegiant Air's Carry-On Fee

    In April 2012 the budget carrier announced a <a href="http://www.huffingtonpost.com/2012/04/02/allegiant-air-carry-on-fe_n_1397911.html" target="_hplink">$35 carry-on fee</a>.

  • Spirit's New Carry-On Fee

    A month later, low-cost Spirit Airlines <a href="http://www.huffingtonpost.com/2012/05/02/spirit-airlines-carry-on-fee_n_1472508.html" target="_hplink">upped carry-on fees to as much as $100</a>.

  • Airlines Could Charge Extra For Seats Together

    Late May 2012 saw airlines start to <a href="http://www.huffingtonpost.com/2012/05/21/airline-charges-seats_n_1533866.html" target="_hplink">reserve more window and aisle seats for passengers willing to pay extra</a>. This would make it it harder for friends and family members to sit next to each other.<br /> <br /> Sen. Chuck Schumer urged airlines to <a href="http://www.huffingtonpost.com/2012/05/27/chuck-schumer-airlines_n_1548794.html" target="_hplink">allow families with young children to sit together without paying extra</a>.

  • United's $100 Bag Fee

    In June 2012, United <a href="http://www.huffingtonpost.com/2012/06/12/united-airlines-raises-international-bag-fee_n_1589223.html" target="_hplink">raised its fee for a second checked bag on trans-Atlantic flights to $100</a>. Delta had done the same a few months earlier.

  • Wizz Air's Carry-On Fee

    Carry-on fees have finally hopped the pond. <a href="http://skift.com/2012/07/09/carry-on-bag-fee-spreading-wizz-air-charge-europe/" target="_hplink">European regional carrier Wizz Air instituted a 10 Euro (about $12) fee to use the overhead bins</a>. Bags that fit under the seats still fly free.

  • Credit Card Booking Fee

    In August 2012, Airefarewatchdog called out <a href="http://www.huffingtonpost.com/george-hobica/the-latest-airline-fee-credit-card_b_1829396.html">Allegiant Airlines for charging more to book flights via credit card</a>.

  • Southwest Airlines' Early Boarding Fee

    <a href="http://www.huffingtonpost.com/2013/01/22/southwest-airlines-fees_n_2525443.html?utm_hp_ref=travel#slide=more232494">Southwest passengers can pay $40 to be one of the first 15 people on the plane</a>, as of January 2013.

  • United Fare Increase

    United Airlines announced in December 2012 that it would be raising domestic fares up to <a href="http://www.huffingtonpost.com/2012/10/10/united-airlines-raises-prices-10-dollars_n_1954864.html" target="_blank">$10 per round trip</a>. While the price bump is minimal, travelers looking for the best deal could be dissuaded from purchasing the slightly more expensive tickets.

  • Allegiant Air

    One of the most profitable airlines in the U.S., <a href="http://www.huffingtonpost.com/2013/06/28/allegiant-air-fees_n_3516384.html" target="_blank">Allegiant Air</a> came into the spotlight for its length list of added-on fees. The budget airline is similar to Ryanair in wooing travelers with low-cost flights to small airports and tacking on hidden fees in every aspect of the flight. In addition to the run-of-the-mill luggage and seat-choice fees, Allegiant has fees for paying with a credit card ($8), using the overhead luggage compartments ($10-$25) and booking over the phone ($50!). (AP Photo/David Becker)

  • American Airline Fare Initiatives

    In response to "nickle-and-diming" complaints, American Airlines introduced new <a href="http://www.huffingtonpost.com/george-hobica/american-airlines-new-fare_b_2312289.html" target="_blank">fare-bundling initiatives</a>. The options -- "choice essential" and "choice plus" -- offer an array of packaged perks for one set price, rather than a la carte. While many complained about the initiative, others saw it as a way to get more for your money.

  • United Premier Access

    United Airlines rolled out "<a href="http://www.huffingtonpost.com/2013/03/01/united-premier-access-rip-off_n_2788513.html" target="_blank">Premier Access</a>" in March 2013. The program includes a designated check-in and security lines, and priority boarding and bagging handling. While the fees for the exclusive services only start at $9, travelers must <em>already</em> be elite customers.

  • Frontier Third-Party "Fees"

    In May 2013, <a href="http://www.cntraveler.com/daily-traveler/2013/05/frontier-airlines-carry-on-fees-050213?MBID=twitter_" target="_blank">Frontier announced</a> that anyone purchasing a ticket through a third-party, such as travel agents or websites like Expedia, would be subject to additional fees. In reality, the fees are actually perks (such as carry-on luggage) Frontier only offers to travelers booking through the airline directly.

  • New Alaska Airline Fees

    In July 2013, <a href="http://www.huffingtonpost.com/2013/07/09/alaska-airlines-fees_n_3568206.html" target="_blank">Alaska Airlines</a> raised its baggage checked fee from $20 per bag (for up to three bags) to $25 per bag for the first two bags, and $75 for an additional piece of luggage. The airline also upped it's ticket-change fee to $125.

  • Spirit's Potential New Fees

    Spirit Airlines is mulling the idea of tying airfare fees to demand. In October, <a href="http://www.huffingtonpost.com/2013/10/31/spirit-airlines-fees_n_4181354.html" target="_blank">the AP reported</a>: "Spirit Airlines is considering tying the fees passengers pay to check a suitcase or pick a more desirable seat to demand. On a peak travel day, for instance, the fees could be much higher. Passengers who booked a Spirit flight for this holiday season can relax however — the changes are months away, if they happen at all."

  • Virgin Atlantic Seat Reservation Fee

    <a href="http://www.huffingtonpost.com/2013/12/17/virgin-atlantic-seat-reservations-fee_n_4459610.html" target="_blank">Virgin Atlantic</a> will start charging travelers $40.65 (£25) per flight to reserve their seats more than 24 hours in advance. Those who aren't picky about where they sit can choose their seat less than 24 hours before the flight at no cost.