track split: Eastbound – Magnetic track 000 to 179° – odd thousands (FL 250, 270, etc.) Westbound – Magnetic track 180 to 359° – even thousands (FL 260, 280, etc.) At FL 290 and above, if Reduced Vertical Separation Minima (RVSM) are not in use, 4,000 ft intervals are used to separate same-direction aircraft (instead of 2,000 ft intervals below FL 290), and only odd flight levels are assigned, independent of the direction of flight: Eastbound – Magnetic track 000 to 179° – odd flight levels (FL 290, 330, 370, etc.) Westbound – Magnetic track 180 to 359° – odd flight levels (FL 310, 350, 390, etc.) Conversely, RVSM equipped aircraft are able to continue separation in 2,000 ft intervals as outlined in the semicircular rules. Both non-RVSM and RVSM equipped aircraft use a separation of 4,000 ft above FL 410. Countries where the major airways are oriented north/south (e.g., New Zealand; Italy; Portugal) have semicircular rules that define a North/South rather than an East/West track split. In Italy, France, Portugal and recently also in Spain (AIP ENR 1.7-3), for example, southbound traffic uses odd flight levels; in New Zealand, southbound traffic uses even flight levels. In Europe commonly used International Civil Aviation Organization (ICAO) separation levels are as per the following table: Quadrantal rule The quadrantal rule is defunct. It was used in the United Kingdom but was abolished in 2015 to bring the UK in line with the semi-circular rule used around the world. The quadrantal rule applied to IFR flights in the UK both in and outside of controlled airspace except that such aircraft may be flown at a level other than required by this rule if flying in conformity with instructions given by an air traffic control unit, or if complying with notified en-route holding patterns or holding procedures notified in relation to an aerodrome. The rule affected only those aircraft operating under IFR when in level flight above 3,000 ft above mean sea level, or above the appropriate transition altitude, whichever is the higher, and when below FL195 (19,500 ft above the 1013.2 hPa datum in the UK, or with the altimeter set according to the system published by the competent authority in relation to the area over which the aircraft is flying if such aircraft is not flying over the UK.) The rule was non-binding upon flights operating under visual flight rules (VFR). Minimum