Southwest Airlines' quarterly revenue missed estimates, partly hurt by a technology outage in July that forced flight cancellations, and the company forecast a key profitability metric to decline in the current quarter.
The company's shares shed 8.46 percent on Wednesday. Southwest Airlines was the worst performer in the Dow transports, which declined 0.65 percent.
Southwest said it expected fourth-quarter unit revenue, a key profitability metric, to decline in the 4-5 percent range.
Deutsche Bank Equity Research analyst Michael Linenberg said he had expected a 2.6 percent decline.
"Our sense is investors were expecting a guide in the down 2-4 percent range," Linenberg wrote in a note to clients.
Rival JetBlue Airways on Tuesday forecast unit revenue to fall 3.5 percent to 4 percent in October.
Southwest said on Wednesday that "while current trends suggest a stabilization of close-in fares, the overall revenue yield environment remains soft."
While more people booked travel on Southwest in the third quarter, fares on average were lower than they were a year earlier, especially for trips booked at the last minute.
A technology outage in July forced Southwest to cancel more than 2,000 flights and offer refunds to passengers. This and bookings trend pushed down the airline's unit revenue 4.1 percent in the third quarter ended Sept. 30.
Southwest said its net income declined to $388 million, or 62 cents per share, in the quarter, from $584 million, or 88 cent per share, a year earlier.
Total operating revenue declined 3.4 percent to $5.14 billion.
Analysts on average had expected earnings of 88 cents on revenue $5.17 billion, according to Thomson Reuters I/B/E/S.