WASHINGTON, March 27 (Reuters) - U.S. senators on

Thursday criticized the Federal Aviation Administration for

failing to act for years to address helicopters in "dangerous

proximity" to commercial airplanes near Reagan Washington

National Airport.

"Why did the FAA not act on 15,000 reports of dangerous

proximity? How were these helicopter routes allowed to remain

when alarm bells were literally going off in the towers?" asked

Senator Maria Cantwell at a Senate hearing on the fatal January

29 collision between an Army helicopter and an American Airlines ( AAL )

regional passenger jet that killed 67 people near Reagan

Washington National Airport.