Definition
DRVSM is the application of Reduced Vertical Separation Minimum (RVSM) within the domestic airspace of the United States, which reduced the required vertical separation between properly equipped and authorized aircraft from 2,000 feet to 1,000 feet at flight levels FL290 through FL410 inclusive. It allows six additional usable flight levels in this altitude band, increasing airspace capacity and fuel-efficient routing options for high-altitude operations.
Plain English
DRVSM is the U.S. version of the rule that lets approved aircraft fly only 1,000 feet apart vertically — instead of 2,000 feet — when cruising between FL290 and FL410. This squeezes more usable altitudes into the busiest part of the upper sky.
Context Anchor
Seen in instrument flying, high-altitude flight planning, and ATC altitude assignments between about 29,000 and 41,000 feet.
Derivation
Domestic refers to airspace within the United States, distinguishing this program from RVSM applied over oceans or in other regions. Reduced Vertical Separation Minimum means the smallest legal vertical gap between aircraft has been reduced — from the older 2,000-foot standard down to 1,000 feet in the specified altitude band.
Why Pilots Care
Operating under DRVSM increases route flexibility and fuel efficiency but requires specific aircraft equipment approval and pilot training.
Intuition Check
“Reduced” does not mean reduced safety or a lower altitude. It means the required vertical gap between approved aircraft is reduced from 2,000 feet to 1,000 feet in that airspace.
Example Sentence 1
The aircraft was certified for DRVSM operations, so the crew filed a cruise altitude of FL370.
Example Sentence 2
Before entering DRVSM airspace the pilot confirmed the aircraft's RVSM equipment was serviceable and current.