The airline has been working to woo back customers who turned to rivals after technology glitches hurt customer service, while handling problems like the grounding of Boeing Co.'s (BA) 787 Dreamliner.
A recent study by Airline Quality Rating, which ranks airlines based on U.S. Department of Transportation figures, said United did the worst job of flying customers in 2012, with the highest complaint rates.
For the first quarter the airline lost $417 million, or $1.26 a share. Revenue rose 1.4 percent to $8.7 billion. After adjusting for merger-related and other charges, the company lost 98 cents for each share. Analysts, on average, were expecting a loss of $1.10 a share, according to Thomson Reuters I/B/E/S.
Last year, United Continental Holdings Inc. (UAL) lost $448 million or $1.36 a share, on revenue of $8.6 billion.
Expenses from aircraft fuel fell 5.5 percent during the quarter, the company said.
Shares of the company closed at $31.34 Wednesday on the New York Stock Exchange.
(Updated at 8:15 a.m. ET)