Shares of United rose as much as 4.2 percent in trading after the bell as the airline's second-quarter profit also topped analysts' estimates.

The third-largest U.S. airline forecast adjusted profit for the full year at between $7.25 and $8.75 per share, up from its previous range of $7.00 to $8.50 per share.

Bigger rivals Delta Air Lines Inc and American Airlines Group Inc have both cut their full-year earnings forecasts in light of rising oil prices.

The Chicago-based carrier cut its plans for capacity growth for the year to a rate of between 4.5 percent and 5 percent, a company spokesman said. It had previously forecast a range of between 4.5 percent and 5.5 percent.

The company said net income fell to $684 million, or $2.48 per share, in the quarter ended June 30 from $821 million, or $2.67 per share, a year earlier, hit by an already-flagged $105 million write-down of the value of its Brazil routes.

On an adjusted basis, the airline earned $3.23 per share, beating analysts' estimates of $3.07, according to Thomson Reuters I/B/E/S.

Total operating revenue rose 7.7 percent to $10.78 billion, while average fares rose 1.5 percent.

Fuel costs, which accounted for a quarter of United's total costs, surged 43.2 percent, reflecting a steep rise in crude oil prices since early 2016.

United said it paid $2.26 per gallon for aircraft fuel on average, up from $1.63 a year earlier.

Shares of the airline have risen 7.7 percent this year, compared with a 13.9 percent fall in the S&P 500 Airlines index <.SPLRCAIR>.

(Reporting by Sanjana Shivdas in Bengaluru; Editing by Anil D'Silva)

By Sanjana Shivdas