RVSM stands for Reduced Vertical Separation Minimum and it changed how high altitude airspace works. Before RVSM, aircraft above 29,000 feet had to stay 2,000 feet apart vertically. Advances in altimeter accuracy and flight control systems made it possible to safely reduce that spacing to just 1,000 feet. By cutting the vertical distance in half, RVSM opened up many more usable flight levels between 29,000 and 41,000 feet. This allows pilots to fly closer to their most fuel efficient altitude, r