Knowing that RVSM would start in Europe around Swanwick's operational launch, National Air Traffic Services (NATS) implemented the new separation system in UK airspace on 19 April 2001 so that the two events would not clash. Because it was not cleared by Eurocontrol to exclude non-RVSM equipped aircraft from the upper flight levels (FL) until 24 January 2002 when RVSM goes live in the other 40 European and two North African countries, NATS allowed compliant aircraft to use any levels in the RVSM band. Non-equipped ones will use the two traditional levels in the band that do not reverse their direction in the new system - FL290 (29,000ft [8,850m]) and FL330. NATS says the transfer was smoother than expected.

Source: Flight International