Shares of Allegiant Travel Co., the parent of Allegiant Air, plunged 13 percent on Thursday on signs that lower fares are taking a toll on the budget airline.

Las Vegas-based Allegiant reported after the market closed Wednesday that third-quarter net income rose 2 percent to $45.5 million.

But Allegiant reported that its average fare, including fees, dropped 9.8 percent from a year earlier. A key measure of revenue for every seat flown one mile dropped 7.4 percent.

Fares have been falling across the airline industry because carriers are adding flights faster than demand is growing, but the decline was sharper at Allegiant.

And the company predicted that the revenue per mile figure would drop by about 6.5 percent in the fourth quarter, a sharper drop than forecast by other airlines. Several analysts also said it was worse than they had expected.

The shares closed down $20 to $133.95. They have fallen 20 percent in 2016.