November 21 marks the start of reduced vertical separation minimums (RVSM) in China’s airspace from FL291 to FL411. That differs from RVSM in much of the rest of the world, where the airspace stretches from FL290 to FL410. China selected the odd flight levels because its military, which controls the country’s airspace, uses metric flight levels. Chinese controllers will continue to issue altitude clearances in meters, but pilots must convert them to feet using a special table. Aircraft equipped only with metric altimeters must obtain special approval to operate in China’s RVSM airspace. ICAO and the FAA assisted China with RVSM implementation, which requires similar aircraft equipment and training as RVSM in other parts of the world.