WASHINGTON, July 16 (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."