The grim forecast for airline profits in 2012 proved true Thursday as United Continental released first-quarter results that showed it lost $286 million largely because of an almost 21 percent increase in fuel costs.

The company said it spent $557 million more on fuel in the first three months of this year than it did during the same period in 2011.

“This was a difficult quarter, but we made significant progress with our integration and we’re now able to serve our customers as a single airline,” said Jeff Smisek, president of United Continental Holdings.

The two airlines completed their merger last winter. The company showed an additional first-quarter loss of $162 million on investment in the merger. By comparison, the company lost $136 million in the first quarter of last year, with an additional charge of $77 million related to the merger.

United is the dominant carrier at Dulles International Airport.

United said ticket revenue increased by 5.5 percent in the first quarter, with total revenue of $8.6 billion, an almost 5 percent increase over 2012.

Tony Tyler, director of the International Air Transport Association, predicted in November that with high fuel prices airlines worldwide would make less than a 1 percent profit in 2012. He said that airlines have lost $25 billion since 2001.