Airlines for America (A4A) said Wednesday that the 10 US passenger airlines that have reported first-quarter results incurred an aggregate net loss of $1.73 billion, down 74% from a net deficit of $1 billion in the March 2011 quarter.

The results mean US carriers operated on a negative 5.2% net margin for the year’s first three months, worse than the negative 3.2% margin on which they operated in the prior-year period.

A4A chief economist John Heimlich noted that the first quarter is traditionally the worst reporting period for US airlines. “Wall Street is expecting most carriers to report modest profitability in 2012,” he said.“With fuel at record-high levels, the financial loss suffered in the first quarter would have been substantially deeper if not for the significant proactive steps that the airlines have taken” to control costs and capacity.

Heimlich said average jet fuel prices are up 7% year to date in 2012, “which is important to note because 2011 was a record high year for spot jet fuel prices.” A4A expects US airlines to operate “slightly fuller” aircraft this summer compared to summer 2011, with load factors projected to average around 85%.