Three senior Democratic lawmakers on Tuesday urged the Federal Aviation Administration to address significant safety issues at Reagan Washington National Airport and maintain reduced air traffic after a series of troubling incidents.

A federal review of helicopter safety around some of the busiest U.S. airports has revealed dangerous flying conditions at the Las Vegas airport.

The FAA said it was addressing several issues at Harry Reid International Airport in Las Vegas involving helicopters, including that tower controllers have not issued traffic advisories between returning air tour helicopters and airplanes, resulting in a routine lack of compliance with separation rules.