Non-RVSM airspace altitude interval selection is typically what?

• A. 1000' intervals
• B. 4000' intervals
• C. 2000' intervals
• D. 6000' intervals

Answer: (B)

Non-RVSM airspace uses standard separation that isn’t reduced by RVSM. To keep a safe and straightforward structure when surveillance and equipment may not be uniformly certified or available, the airspace is typically divided into layers spaced about 4000 feet apart. This larger interval provides a robust buffer between flight levels in non-RVSM conditions and aligns with traditional, conservative spacing used when reduced vertical separation isn’t in effect. The tighter 1000-foot spacing would only apply within RVSM airspace, while 2000-foot spacing is common in some contexts but not the usual interval described for non-RVSM planning in this question. A 6000-foot gap would be impractically wide and inefficient for routine routing.