Delta Air Lines Inc (DAL.N) on Thursday reported a second-quarter profit above analysts' expectations and promised more curbs to its flight capacity growth to help offset a decline in a closely watched revenue measure.

The No. 2 U.S. airline by passenger traffic said earnings rose 4 per cent to US$1.55 billion.

Excluding special items such as the settlement of fuel hedges, the profit came to US$1.47 per share. Analysts on average expected US$1.42, according to Thomson Reuters I/B/E/S.

Delta said it would increase its flight capacity - its seats and how far it flies them - one percentage point less than it previously expected for the fourth quarter to match reduced demand.

U.S. airfares close to departure dates are lower than they were a year ago.

That, along with sales in foreign currencies weakening against the U.S. dollar, has contributed to a decline in passenger unit revenue for more than a year. The measure fell 4.9 per cent in the second quarter from a year earlier, and Delta expects a drop of 4 per cent to 6 per cent for the third quarter.

"We remain focused on achieving our goal of positive unit revenues by year-end," President Glen Hauenstein said in a news release.