Delta Air Lines Inc expects a solidly profitable second quarter as higher revenues have for the most part offset rising fuel costs.

The airline said in a U.S. Securities and Exchange Commission filing on Monday it expects an operating margin of 6.5 percent to 7 percent for the second quarter. Passenger unit revenue is expected to be up 10 percent.

Delta's non-fuel unit costs were running higher than expected because of rising maintenance costs and lower-than-planned capacity.

To keep costs down, Delta has taken a host of moves including offering a voluntary exit plan for which 55,000 of its workers are eligible; consolidating facilities in certain U.S. locations; and plans to accelerate the retirement of least fuel-efficient planes.

Delta also repeated that it will cut its system capacity by 4 percent after the Labor Day holiday, with U.S. capacity down 1 to 3 percent and international falling 4 percent to 6 percent.

(Reporting by Karen Jacobs; Editing by Derek Caney)