The International Civil Aviation Organization (ICAO) has recommended a transition to using the International System of Units since 1979[13][14] with a recommendation on using metres (m) for reporting flight levels.[15] China, Mongolia, Russia and many CIS countries have used flight levels specified in metres for years. Aircraft entering these areas normally make a slight climb or descent to adjust for this, although Russia and some CIS countries started using feet above transition altitude and introduced RVSM at the same time on 17 November 2011.