Delta Air Lines Inc (DAL.N) on Tuesday cut its forecast for passenger unit revenue, a closely watched performance metric, for the current quarter due to slower than anticipated recovery in fares for last-minute flights.

The No. 2 U.S. airline by passenger traffic said it now expects third-quarter passenger unit revenue, which compares sales to flight capacity, to rise 2-3 per cent.

It had previously forecast an increase of 2.5-4.5 per cent.

Delta also cut its operating margin forecast to 16.5-17.5 per cent from 18-20 per cent for the quarter.

The company's shares were down 1.7 per cent at US$46.71 in premarket trading.