AMR Corp.'s American Airlines, Continental Airlines Inc., UAL Corp.'s United Airlines, US Airways Group Inc., JetBlue Airways Corp. and Delta Air Lines Inc. matched the Southwest prices, officials at those carriers said.
A three-day sale by AirTran ended Thursday night.
Dallas-based Southwest launched the sale shortly after announcing Thursday that it lost money in the fourth quarter, its second-straight losing quarter after 69 straight profitable ones.
Chief Executive Gary Kelly said Thursday that there was "notable softness" in February and March bookings. The day before, AMR Chief Financial Officer Thomas Horton said March looked particularly weak.
Airlines often match their rivals' fares rather than risk losing price-sensitive passengers.
Last year, airlines raised prices several times and imposed new fees on checked bags to counter rising fuel prices. Although fuel prices have fallen sharply, most of the fees are still in effect.