Definition
DRVSM is the application of Reduced Vertical Separation Minimums (RVSM) within the domestic airspace of the United States, allowing properly equipped and authorized aircraft to be vertically separated by 1,000 feet — instead of the previous 2,000 feet — between Flight Level 290 (FL290) and Flight Level 410 (FL410) inclusive. Aircraft and operators must meet specific altitude-keeping equipment, monitoring, and authorization requirements to operate in DRVSM airspace.
Plain English
In the high-altitude block from 29,000 to 41,000 feet over the U.S., approved aircraft can fly just 1,000 feet apart vertically instead of 2,000 feet. This lets more aircraft use the most efficient cruise altitudes at the same time.
Context Anchor
You may see DRVSM in instrument procedure references, high-altitude flight planning, aircraft equipment discussions, and ATC-related material for flights above 29,000 feet.
Derivation
‘Domestic’ here simply means within U.S. airspace, distinguishing it from RVSM programs in oceanic or foreign airspace. ‘Reduced’ refers to the change from the older 2,000-foot standard to 1,000 feet. ‘Vertical separation minimums’ are the smallest legal vertical distances ATC must maintain between aircraft.
Why Pilots Care
Approved aircraft gain access to more usable altitudes, improving routing options, fuel efficiency, and airspace capacity.
Analogy
It is like allowing cars to use lanes that are closer together only if the cars and drivers meet stricter standards. The space is smaller, so the equipment and control have to be more precise.
Intuition Check
Do not read “reduced” as meaning safety is reduced. It means the required vertical spacing is smaller because aircraft and procedures must meet stricter standards.
Example Sentence 1
Because the aircraft was DRVSM-approved, the crew was able to file for FL350 and stay at the most fuel-efficient altitude for the cruise.
Example Sentence 2
Only aircraft with current DRVSM approval may file for the reduced vertical separation levels.