CHICAGO (AP) — United Airlines passenger revenue fell in August for the first time since early last year despite a slight increase in traffic.

The airline, which is operated by United Continental Holdings Inc., said late Monday its passenger revenue per available seat mile fell by an estimated 0.5 percent to 1.5 percent from a year ago.

That figure measures how much money the airline makes to fly a paying passenger a single mile. United said last week its share of lucrative corporate fliers has been less than it expected because of problems resulting from the blending of operational systems from United and Continental following their merger.