Reduced Vertical Separation Minima (RVSM) Phase 1

RVSM is an aviation standard that reduces the required vertical separation between aircraft from 2,000 feet to 1,000 feet between flight levels FL290–FL410. This effectively doubled the number of usable cruising altitudes, improving airspace capacity and fuel efficiency.

Phase 1 was essentially a controlled trial (operational evaluation) to validate safety, aircraft performance, and monitoring systems before wider adoption. It applied initially to flight levels  FL330–FL370 (33,000–37,000 ft), was conducted in North Atlantic Minimum Navigation Performance Specification (MNPS) airspace, and only specially equipped and approved aircraft were allowed to participate.