I understood that non-ICAO phrases used in the UK were to avoid some of the misunderstandings which can exist in ICAO phraseology and which have been shown to pose a flight safety risk. I know that they have all been carefully scrutinised before being implemented and have been notified as being non ICAO standard phrases.
On a completely separate point, I always have a chuckle in the USA when pilots say 'oh' as a numeral and controllers (nearly) all say zero.
Last edited by beardy; 27th Aug 2012 at 10:22.