The Air Navigation (Overseas Territories) Order 1989

Quadrantal Rule and semi-circular Rule

26.  In order to comply with the Instrument Flight Rules, an aircraft when in level flight above 3,000 feet above mean sea level or above the appropriate transition altitude, whichever is the higher, shall be flown at a level appropriate to its magnetic track, in accordance with the appropriate Table set forth in this Rule. The level of flight shall be measured by an altimeter set according to the system published by the competent authority in relation to the area over which the aircraft is flying:

Provided that an aircraft may be flown at a level other than the level required by this Rule if it is flying in conformity with instructions given by an air traffic control unit or in accordance with notified en-route holding patterns or in accordance with holding procedures notified in relation to an aerodrome.

For the purposes of this Rule “transition altitude” means the altitude so notified in relation to flight over such area or areas as may be notified.

TABLE I—Flights at levels below 24,500 feet

Magnetic Track	Cruising Level
Less than 90°	Odd thousands of feet.
90° but less than 180°	Odd thousands of feet + 500 feet.
180° but less than 270°	Even thousands of feet.
270° but less than 360°	Even thousands of feet + 500 feet.

TABLE II—Flights at levels above 24,500 feet

Magnetic Track	Cruising Level
Less than 180°	25,000 feet.
	27,000 feet.
	29,000 feet or higher levels at intervals of 4,000 feet.
180° but less than 360°	26,000 feet.
	28,000 feet.
	31,000 feet or higher levels at intervals of 4,000 feet.