Quoting Fawlkes:
"By all means salute the Prime Minister, but address him as Mr Blair, not, as he would wish, Tony, or Sir."
Sorry chap, but that's incorrect. And what "he wishes" doesn't come into it. There are rules, and they are very simple:
1: He IS to be saluted. He is the appointed head of Her Majesty's Government, so recieves a salute whether you happen to like him or not. This is equally applicable to all members of the Cabinet. (But not to the opposition).
2: He is addressed as "Prime Minister" in the first instance, "Sir" in any following converation. All other cabinet ministers are addressed similarly as "Minister" then "Sir".
3: All of this applies notwithstanding your own personal feelings on matters political.. It's in the rules, it's not left down to your own whims on whether you like someone or not. After all, do you only salute senior Officers that you like personally, or respect?
(And in response to the original question):
4: The nice young lady at Northolt who saluted the PM was no doubt the duty Protocol Officer or Movements Officer. It is common courtesy to have the Station Commander or a nominated deputy present at all movements involving a VVIP at an RAF airfield. Regardless of who's operating the flight.
Has no-one here ever been involved in a VIP visit to their station? The 5 pages of rubbish so far on this subject would seem to indicate so.