The address, if a formal letter, should state the whole rank, Title, name and/or initials, surname and decorations, ending in RAF or RAF (Retd) as appropriate. Abbreviations may be used but should then be used throughout the body of the letter too, including the date. This is the old-school Service way of things though there are newer approaches I understand. Example 1: AVM Sir John Smith, AFC, BA, RAF The Lodge Crinkling in the Wold Example 2: Air Vice Marshal IM Grate VC, DFC, AFC, RAF (Retired) Etc, etc
Normally, Air-Chief-Marshal Exceptionally, Marshal of the Royal Australian Air Force¹
The Royal Air Force rank of Air Marshal is equivalent to Vice-Admiral (Royal Navy) and Lieutenant-General (British Army and Royal Marines).
An Air Chief Marshal is someone who belongs to the most senior rank active in the Royal Air Force.
An Air Vice-Marshal is a rank in the Royal Air Force, between air commodore and air marshal, equivalent to an army major general.
An Ardian is a proposed but unadopted air-officer rank of the Royal Air Force, equivalent to air vice-marshal.
Marshall Royal died on May 19, 1995, in Los Angeles, California, USA.
The former Air Vice-Marshal of the British Royal Air Force, Michael Lloyd, is straight.
Marshall of the Royal Air Force. This rank however is only given out during wartime or if an RAF officer is Chief of the Defence Staff (head of all British Armed Forces) The highest rank to which officers on active service are promoted is now Air Chief Marshall
An air commodore is a rank in the Royal Air Force between group captain and air vice-marshal, or an officer holding this rank.
First time your Royal Highness, then after that, Madam.
In a letter you would begin: "May it please Your Majesty"
Air Chief Marshal Dowding and Air Chief Marshal Harris were connected in the sense that both were fighter pilots in the Royal Flying Corps in WW1 and 20 + years later in WW2, were the Commanders of Fighter Command and Bomber Command in the Royal Air Force. - Both were quite controversial and had unorthodox methods - but got the job completed successfully.