The FAA plans to begin a safety evaluation of domestic reduced vertical separation minimums (DRVSM) next month in an effort to show that the planned transition in U.S. airspace can be made without risk. FAA officials said the agency still plans to issue an NPRM in the spring that would reduce vertical airspace separation between FL 350 and FL 390 from the current 2,000 ft to 1,000 ft. Eventually, full DRVSM would be expanded to include all the airspace between FL 290 and FL 410. The first phase of DRVSM is scheduled for implementation in late 2004.