Definition
The application within U.S. domestic airspace of 1,000 feet vertical separation between aircraft operating at flight levels FL290 through FL410 inclusive, in place of the 2,000 feet that previously applied above FL290. Aircraft and operators must hold specific RVSM authorization, with qualifying altitude-keeping equipment and approved operating procedures, in order to fly within DRVSM airspace.
Plain English
It is the rule, used in U.S. domestic airspace, that lets properly approved aircraft fly only 1,000 feet apart vertically between FL290 and FL410, instead of the older 2,000-foot spacing. Aircraft without the right equipment and approval cannot fly in this airspace.
Context Anchor
Seen in instrument flying, high-altitude flight planning, aircraft equipment requirements, and ATC altitude assignments above 29,000 feet.
Derivation
Domestic' here means within the United States (as opposed to oceanic or international). 'Reduced' refers to cutting the older 2,000-foot vertical buffer in half. Naming it this way distinguishes the U.S. program from the earlier oceanic RVSM rules, which were introduced first.
Why Pilots Care
It increases the number of usable flight levels, allowing more efficient routing and reduced fuel consumption in busy domestic airspace.
Grounding Statement
The key idea is that ATC can safely fit more approved aircraft into high-altitude airspace by using 1,000-foot vertical spacing instead of 2,000-foot spacing.
Intuition Check
“Domestic” does not mean every flight within the United States; it means specified U.S. domestic RVSM airspace. “Reduced” does not mean less safe; it means the allowed vertical spacing is smaller because approved aircraft can hold altitude accurately enough.
Example Sentence 1
Before climbing to FL350, the crew confirmed the aircraft was DRVSM authorized and that the altitude-keeping equipment was operating normally.
Example Sentence 2
Before departure the crew verified the aircraft met all requirements for Domestic Reduced Vertical Separation Minimum operations.