American Airlines said its passenger traffic was up 2.2 percent in June as the carrier increased its capacity by 2.8 percent.
However, planes were not as full as its load factor dropped 0.5 percentage points to 84.9 percent.
The company told investors that it expects unit revenues for the second quarter to be down about 6 to 7 percent compared to the same quarter last year.
American also revised its full year capacity guidance, telling Wall Street that it expects its total system capacity to be up 2 percent instead of its previous estimate of 2.5 percent for 2016.
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The carrier said it expects to pay an average of $1.39 to $1.44 for a gallon of mainline jet fuel. It ended the quarter with $7.1 billion in unrestricted cash and investments.
American will announce its second quarter earnings on Friday, July 22.