Basic Area Navigation Below FL95

Basic Area Navigation (B-RNAV) was introduced on the UK ATS route structure during April 1998. The ECAC Navigation Strategy had intended RNAV at all en-route flight levels; however, due to equipage problems with older commercial air transport and general aviation aircraft, the UK and other States introduced B-RNAV above FL95 only. This has resulted in constraints in achieving maximum airspace efficiency, where the retention of an ATS route structure below FL95 referenced to ground-based navigation aids (VOR or NDB) restricts design options. Moreover, retention of these arrangements precludes any future rationalisation of the ground navigation infrastructure.