Passenger traffic slipped 1% in July, but revenue at U.S. commercial airlines still rose nearly 20% compared to year-earlier levels, according to figures from the Air Transport Association. Even that strong revenue gain fell short of June's numbers, the group noted. "Demand for air travel remains well above last year's depressed levels, but the industry is mindful of cautionary notes about the health of the overall economy," ATA President and CEO James May said in a statement. In a separate 2010 economic report, the association said the airline recovery appeared fragile and the profit outlook was uncertain. "Put simply, the U.S. airline industry continues to be confronted by a systematic inability to cover its cost of investor capital or ... to exceed break-even profitability on a sustainable basis," the report noted.