WASHINGTON (Reuters) - Major U.S. aviation groups and unions urged Congress to address persistent shortfalls in funding for Federal Aviation Administration facilities after a series of reports raised alarm about aging air traffic control facilities.

"Necessary maintenance of existing systems is being neglected," said the letter signed by Airlines for America, Aerospace Industries Association, the U.S. Chamber of Commerce, Air Line Pilots Association and others warning a failure to address funding needs "will mean reduced airspace operational efficiency -- negatively affecting the traveling public and other civil and military users of the system."