US Airways' consolidated passenger revenue per available seat mile (PRASM) fell by 4% in April, its first decline in more tham three years.
The Tempe, Arizona-based carrier cited "unpredictable operational challenges" related to the sequester and slackening demand for the decrease.
US Airways' passenger unit revenue last fell in December 2009, when it declined about 2% year-on-year.
Consolidated traffic was up 4.4% and capacity 3.1% in April versus a year earlier. The load factor was up 1.1 percentage points to 83.6%.
Domestic traffic grew 6.6%, Atlantic traffic decreased by 2% and Latin traffic fell by 2.4% during the month.
Domestic capacity grew 3.2%, Atlantic capacity rose 3.6% and Latin capacity increased 1.1% in April.