DALLAS — Airlines stocks were pummelled Thursday after Delta Air Lines Inc. trimmed its revenue forecast for the fourth quarter, renewing investors’ fears that airlines will squander the savings they are reaping from the recent drop in fuel prices.

Delta shares plunged nearly 9 per cent, their worst one-day showing since 2012, to close at $45.61.

The parent companies of American Airlines, United Airlines and Alaska Airlines all dropped about 5 per cent or more.

Delta, the nation’s No. 2 carrier by traffic, said that a closely watched figure of revenue per mile rose about 3 per cent in the fourth quarter, a half-point lower than Delta predicted last month and a full point below its October forecast.

The Atlanta-based airline said prices for tickets sold close to departure – often at higher prices – rose less than expected in late December.

Delta said travel demand remained healthy, but its revised revenue outlook fanned fresh fear of weaker airline pricing power seeping into 2019, especially if global economic growth slows.

Airlines raised fares to cover surging fuel prices during the first nine months of 2018, but fuel prices have fallen sharply since early October, which could encourage fare wars by lowering one of the airlines’ major expenses.

“In the past, the airlines have competed away gains from lower fuel as they reward customers with lower fares,” Cowen analyst Helane Becker said in a note to clients. “With oil trending lower in recent months, investors are worried this time will not be different.”

JP Morgan analyst Jamie Baker said stock-market volatility could be hurting airline bookings. He said gloomy financial headlines – the Standard & Poor’s 500 index has dropped 14 per cent in the last three months – make people less likely to plan a lavish vacation.