American said Tuesday that paying passengers flew 11.46 billion miles last month, down 0.4 percent from 11.51 billion miles in August 2010.
Domestic travel, which accounts for nearly three-fourths of the company's operations, dropped 2.6 percent, while international traffic rose 3 percent, mostly because of strong trans-Pacific travel.
American reduced passenger capacity by 1.2 percent, to 13.45 billion available seat miles, which is one seat flown one mile. Airlines often reduce capacity by cutting flights.
With capacity falling faster than traffic, the average plane was slightly more full. Occupancy averaged 85.3 percent, up from 84.6 percent a year earlier.
Unlike Delta and US Airways, American did not disclose Tuesday how much it lost from last month's Hurricane Irene that caused the cancellation of thousands of flights on the East Coast.
Delta said it lost $15 million from the storm, and US Airways estimated its losses between $8 million and $10 million.
On American, traffic for the first eight months of the year was running 1.4 percent higher than the same period last year. Capacity was up 1.7 percent, and average occupancy fell to 82 percent from 82.2 percent last year.
Shares of parent AMR Corp. fell 10 cents, or 2.9 percent, to close at $3.32.