RAF Centennial

Today, 1 April 2018, marks the 100th anniversary of the Royal Air Force, formed by combining the Royal Naval Air Service and the Royal Flying Corps.
By the end of the war the RAF had 291,000 officers and men and 22,647 aircraft.
The heyday of the RAF was during the Second World War with Churchill referring to the RAF and the Battle of Britain.

Never in the field of human conflict was so much owed by so many to so few.

The Canadian Air Force, formed on 17 May 1920 with the prefix Royal added in 1924 was integral to RAF operations in WW2.
Of 124,356 Air Force causalities 17,395 were Canadian.

The (UK) National Archives has a handy guide to RAF Personnel Records. Digitized records, all pre-WW2 are:

Ancestry
UK, Royal Air Force Airmen Records, 1918-1940, 616,118 records
UK, Royal Air Force Muster Roll, 1918, 194,814 records
Web: UK, Women's Royal Air Force Index, 1918-1920, 31,086 records.

Findmypast
British Royal Air Force, Airmen's Service Records 1912-1939, 342,825 records
British Royal Air Force, Officers' Service Records 1912-1920, 101,266 records
British Women's Royal Air Force Service Records 1918-1920, 31,090 records
Royal Air Force Muster Roll 1918, 181,625 records.

TheGenealogist
Air Force Lists for Apr 1918, Oct 1933, May 1936, Apr 1937, Sep 1938, Jan 1939, June, 1939, May 1940.
Monthly Air Force List, November 1921.

Note: More issues of The Air Force List for the WW2 period are available free on The Internet Archive.

You may be interested in the12 part Century of the RAF on YouTube.