What is RVSM? ​

RVSM stands for Reduced Vertical Separation Minimum. It allows aircraft flying between FL290 and FL410 to be separated by 1,000 feet instead of the old standard of 2,000 feet. This effectively doubled the number of usable flight levels in the busiest altitude band.

The problem it solved ​

Before RVSM, vertical separation above FL290 was 2,000 feet. That meant the only usable flight levels were FL290, FL310, FL330, FL350, FL370, FL390, and FL410. Seven levels for all the traffic in the upper airspace.

This was a bottleneck. Most jets want to cruise between FL310 and FL390 where fuel burn is lowest. With only a few levels available, controllers constantly had to refuse requested altitudes or hold aircraft at inefficient lower levels.

What changed ​

RVSM was implemented in Europe in 2002 and in the US in 2005. It added flight levels in between the old ones: FL300, FL320, FL340, FL360, FL380, FL400. The usable levels between FL290 and FL410 went from 7 to 13.

More levels means more room. Controllers can assign closer-to-optimal altitudes, approve more direct routings, and handle higher traffic volumes without running out of vertical space.

Equipment requirements ​

The reason 2,000 feet was needed in the first place was altimeter accuracy. At high altitudes, older altimeters could be off by several hundred feet. Two aircraft both "at FL350" might actually be 300 feet apart.

RVSM-approved aircraft must have:

• Two independent altimeter systems
• An altitude alerting system
• An automatic altitude-keeping system (autopilot with altitude hold)
• Altimeter accuracy within 65 feet at cruise

The aircraft also needs specific maintenance checks and monitoring to stay RVSM-approved. If the autopilot fails or altimeter accuracy degrades, the aircraft loses RVSM approval and must leave RVSM airspace or request 2,000 feet of separation.

Non-RVSM aircraft ​

Aircraft without RVSM approval can still fly above FL290, but they need special handling. The controller must provide 2,000 feet of separation above and below them. This essentially blocks two flight levels instead of one, so controllers prefer to keep non-RVSM aircraft below FL290 when possible.

State aircraft (military) and some older aircraft types are the most common non-RVSM flights.

Above FL410 ​

RVSM only applies up to FL410. Above that, vertical separation goes back to 2,000 feet (or 1,000 feet in some newer implementations). Very few commercial flights cruise above FL410 - it's mostly business jets and a few long-haul flights at light weights.

In radarcontrol.io ​

The sim uses 1,000 feet of vertical separation at all altitudes - RVSM is assumed for all aircraft. There's no distinction between RVSM-equipped and non-RVSM aircraft, and you won't encounter situations where an aircraft needs 2,000 feet of vertical separation.

In the real world, controllers occasionally deal with non-RVSM aircraft that require extra spacing. The sim simplifies this so you can focus on lateral separation and sequencing without worrying about equipment-based altitude restrictions.

The semicircular rule still applies: eastbound traffic gets odd flight levels (FL310, FL330, FL350), westbound gets even (FL320, FL340, FL360).

Related: What is a flight level? | What are aircraft categories? | How does ATC separation work? | What are airways?

Guides: Command reference | Quick start guide

Play London Center - manage traffic across the busiest RVSM airspace in Europe.