The US carrier reported a pre-tax profit of $494 million for the three months to the end of March, down from $511 million in the previous year.
Revenue was down 4.8% year-on-year to $8.2 billion. Fuel costs fell 34.7% to $1.2 billion.
Meanwhile, parent company United Continental Holdings has reached an agreement with two of its investors over new board appointments.
Two people proposed by Altimeter Capital Management and PAR Capital Management, who collectively own 7.1% of the airline group, will join the board with immediate effect.
