Definition
An air traffic control standard that reduces the required vertical spacing between aircraft from 2,000 feet to 1,000 feet in the airspace between Flight Level 290 and Flight Level 410. To operate in this airspace, aircraft must be specially equipped with high-precision altitude-keeping equipment and the operator must be certified for these operations.
Plain English
A rule that lets properly equipped aircraft fly with only 1,000 feet of vertical space between them at high altitudes, instead of the older 2,000-foot gap. This packs more aircraft into the most fuel-efficient altitudes.
Context Anchor
You will see this term in high-altitude IFR flight planning, ATC procedures, aircraft equipment requirements, and clearances involving flight levels above FL290.
Derivation
Reduced' means made smaller. 'Vertical separation' is the up-and-down distance between aircraft. 'Minimum' is the smallest amount allowed. Together: the smallest legal vertical gap, made smaller than it used to be.
Why Pilots Care
Increases the number of available flight levels and allows more efficient routing without reducing safety margins.
Grounding Statement
If one approved aircraft is flying at FL350, another approved aircraft may be assigned FL360, only 1,000 feet above it.
Intuition Check
“Reduced” does not mean separation is casually made smaller everywhere. It means the required vertical spacing is reduced only in specific high-altitude airspace and only for aircraft approved to use it.
Example Sentence 1
The aircraft was certified for reduced vertical separation minimum operations, so the crew could file a cruise altitude of FL350.
Example Sentence 2
Flight planning software automatically applies Reduced Vertical Separation Minimum altitudes when routing through the approved region.