Delta Chief Will Retire

Delta Air Lines chief executive Ronald W. Allen, who led the carrier into a costly European expansion and an aggressive cost-cutting campaign, will leave the nation’s third-largest carrier at the end of July.

Delta said Monday that Allen, 55, was retiring and would resign from the board of directors. The surprise move coincides with the expiration of Allen’s current employment contract on July 31.

Maurice W. Worth, the 56-year-old executive vice president for customer service, was named the acting chief operating officer and given day-to-day authority to run the airline.