Delta Air Lines has become the second large US carrier to report a loss for the three months to end-March.

The number-three US airline posted a net loss of $397m, almost exactly trebling its loss from a year earlier.

On Monday, smaller rival Continental reported a $166m net loss.

Customers and revenues were returning, but revenues were recovering at a slower pace, the airline said.

The airline warned that lingering weakness in the business travel market - a key source of high-margin earnings - would affect the pace of its recovery.