At the outbreak of war bomber aircrew were almost completely Royal Air Force or Royal Air Force Volunteer Reserve or Auxiliary Air Force although a number of commissioned officers of the RAF were Canadians, Australians, New Zealanders, Rhodesians and South Africans.
By 1941 bomber crews included men of the Royal Canadian Air Force, Royal Australian Air Force or Royal New Zealand Air Force and by 1942 there were entire squadrons of those Commonwealth Air Forces in which a very substantial percentage of the airmen were from the parent countries.