If there was any doubt that lower oil prices were a gift to the nation’s big airlines, just check out the latest results and outlook from Delta.

Delta CEO Richard Anderson said in a statement that lower fuel prices should save the company more than $2 billion this year.

The airline is already doing well. Delta reported a fourth-quarter profit, excluding one-time charges, that topped expectations Tuesday.

Shares of Delta rose over 3% in early trading on the news.

The forecast for Delta looks even sunnier. Delta promised strong profit margins for the first quarter and predicted earnings growth in the double digits for the full year.

Delta, along with other airlines, were among the top performers on Wall Street last year thanks largely to lower fuel costs. The stock gained nearly 70% in 2014.

Southwest, which will report earnings on Thursday, soared about 120% last year, making it the top performer in the SP 500. Its shares rose on Tuesday morning as well.

So did the stocks of rivals United Continental, American, JetBlue and Alaska Air. Those four airlines will also report their latest results in the coming days.

Shares of smaller airlines Spirit and recent IPO Virgin America also gained altitude on Tuesday.

But while the sudden plunge in fuel costs is sure to help the airlines for the rest of the year, Delta did take a hit in the fourth quarter as a result of how fast they fell.

The airline technically reported a loss due mostly to a $1.2 billion charge it took to adjust for the cost of fuel-hedging contracts that had been set up in anticipation of higher energy prices.

Most airlines use such hedges so they don’t get caught off guard by a big spike in fuel costs.

Still, it appears that investors are more excited about the possibility of cheaper fuel in the future than about the hedging mishap.

Lower energy prices also mean that consumers and business travelers are more willing to fly as well. To that end, Delta said that its revenues were up nearly 6% in the fourth quarter.

Passenger revenue in the United States surged nearly 11%, a clear sign that Americans are taking to the friendly skies in droves.

But the increase in Delta’s overall sales was higher than the increase in passenger traffic and capacity. That shows that Delta and other airlines are also doing well thanks to a litany of surcharges that travelers are now forced to pay.

So it will be interesting to see if lower fuel prices eventually lead to lower fares now that the airlines are raking in big profits.