Editing Flight level (section)

==Quadrantal rule==
The quadrantal rule is defunct.<ref>{{Cite web |url=https://www.caa.co.uk/Commercial-industry/Airspace/Rules-of-the-air/SERA-Implementation/ |title=SERA Implementation &#124; UK Civil Aviation Authority |access-date=19 September 2019 |archive-date=7 August 2019 |archive-url=https://web.archive.org/web/20190807012711/http://www.caa.co.uk/commercial-industry/airspace/rules-of-the-air/sera-implementation/ |url-status=dead }}</ref> 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.<ref>{{cite web|url=http://www.caa.co.uk/sera|title=Standardised European Rules of the Air – UK Civil Aviation Authority|publisher=Civil Aviation Authority|access-date=20 August 2016}}</ref><ref>{{cite web |url=http://flyontrack.co.uk/wp-content/uploads/2015/02/SERA.pdf |title=SERA – all you need to know |author=Dave Drake, CAA Project Lead for SERA  |publisher=flyontrack.co.uk |access-date=20 August 2016}}</ref>

The quadrantal rule applied to [[Instrument flight rules|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&nbsp;ft above mean sea level, or above the appropriate transition altitude, whichever is the higher'', and when ''below FL195'' (19,500&nbsp;ft above the 1013.2&nbsp;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.){{citation needed|date=September 2019}}

The rule was non-binding upon flights operating under [[visual flight rules]] (VFR).

Minimum vertical separation between two flights abiding by the UK Quadrantal Rule is 500&nbsp;ft (''note these are in [[Geopotential height|geopotential]] foot units''). The level to be flown is determined by the magnetic track of the aircraft, as follows:<ref>Rules of the Air Regulations 2007 (No. 734), rule 34, table 1. Available from the [http://www.statutelaw.gov.uk UK Statute Law Database.]</ref>

* Magnetic track 000 to, and including, 089° – odd thousands of feet (FL070, 090, 110 etc.)
* Magnetic track 090 to, and including, 179° – odd thousands plus 500&nbsp;ft (FL075, 095, 115 etc.)
* Magnetic track 180 to, and including, 269° – even thousands of feet (FL080, 100, 120 etc.)
* Magnetic track 270 to, and including, 359° – even thousands plus 500&nbsp;ft (FL085, 105, 125 etc.)