Southwest Airlines Co. and its AirTran Airways subsidiary have launched a sale that includes fall flights starting at $99 per round trip.
Tuesday's sale appeared designed to fill seats on planes after the peak summer travel season ends and families return home for the start of the school year.
Dallas-based Southwest and AirTran said they were charging $49 each way on flights of 500 miles or less, $99 each way for 501 to 1,300 miles, and $139 each way for trips longer than 1,300 miles.
Southwest and other airlines have raised their base fares more than a dozen times since the start of 2011 to cope with rising prices for jet fuel -- their top expense. But government figures show spot prices for jet fuel have dropped by nearly one-fifth since April 1.