Most airline stocks have lost altitude in 2015, but they rallied Friday on signs that carriers may soon raise fares at the same time that energy prices are heading lower.

Delta apparently started a fare hike of $2 each way on many domestic flights, according to J.P. Morgan. And FareCompare.com said Friday that JetBlue and others had raised prices by $1 to $4 each way on a smattering of routes.

It was unclear whether the increases would stick. They could be rolled back if discount airlines like Southwest follow suit, but Wall Street did not wait to pile in after last week's increase of $5 each way on many tickets.

"We are surprised to see Delta lead off an additional broad-based effort so soon after the industry's last success," J.P. Morgan analyst Jamie Baker wrote. "But we see no harm in trying."

On Friday, the price of benchmark U.S. crude fell $1.06 to $59.39 per barrel on the New York Mercantile Exchange. Cheaper oil could translate to lower spot prices for jet fuel, a major expense for airlines.

In afternoon trading, shares of American Airlines Group Inc. were up $1.775, or 4.4 percent, to $41.75; United Continental Holdings Inc. gained $1.71, or 3.3 percent, to $53.72; Delta Air Lines Inc. rose $1.07, or 2.6 percent, to $42.42; Southwest Airlines Co. gained 31 cents to $34.17; and JetBlue Airways Corp. was up 54.5 cents, or 2.7 percent, to $20.505.

At the beginning of the session, the Arca index of airline stocks was down 9 percent in 2015 after gaining 49 percent last year.

The drop has been even sharper at major U.S. carriers. Through Thursday, American had lost 25 percent in 2015, United shares were down 22 percent, Delta was off 16 percent and Southwest was down 20 percent. JetBlue, which has bucked a downward trend in the industry by reporting gains in a key revenue figure, rose 26 percent through Thursday.