Delta Air Lines Inc. plunged the most in more than three years, pulling rivals lower, after disappointing ticket pricing forced the carrier to cut its revenue forecasts for the second time in two months.

Fourth-quarter revenue from each seat flown a mile, or unit revenue, will rise 3 percent from a year earlier, the Atlanta-based airline said in a regulatory filing Thursday. Delta previously forecast a 3.5 percent gain.

The news added to investor concerns that weaker pricing and the possibility for slowing global demand from trade wars could weigh on profits this year. The timing—coming only three weeks after Delta’s last update Dec. 13 and following the busy holiday travel season—may have magnified investors’ alarm, said Savanthi Syth, a Raymond James Financial Inc. analyst.

The revenue reductions are coming “from two of the most important weeks in the quarter,” Syth said. “This is just one of those shoot first and ask questions later, as in, this is a confirmation of all the fears.”

The stock sell-off seems like an overreaction, she said. “Cooler minds would wait to see what other airlines have to say.” Delta is the first major carrier to comment on December trends.

The unit-revenue change would reduce the previously expected $1.30 per-share profit last quarter by about 4 cents, Syth estimates. Delta will officially report financial results later this month.

Delta dropped 8.8 percent to $45.67 at 11:31 a.m. in New York after tumbling as much as 10 percent, the most intraday since August 2015. Other carriers fell sharply as well, bringing a Standard & Poor’s index of airlines down 6.7 percent, the worst performing group on the S&P 500. The rout came amid a broad slump after Apple cut its sales outlook and weak U.S. manufacturing data was released.

“The pace of improvement in late December was more modest than anticipated,” Delta said of average fares per mile. Demand from business and leisure travelers remained “healthy” in the quarter, it said. Total revenue will rise about 7 percent instead of the 7.5 percent that had been expected.

Given the timing of Christmas in 2018, investors may have expected that business travel would stay strong through December 21, said Helane Becker, a Cowen Inc. analyst. “That appears not to have happened for Delta,” she said in a note to investors.

The airline narrowed its outlook for fourth-quarter profit to $1.25 to $1.30 a share, the high end of its earlier expectation