Australia having declared war on Germany on 3 September 1939, the RAAF
Air Board met in November to discuss Bell's letter, but postponed taking action. She continued to lobby, as did several other women's groups seeking to support the war effort and free male staff for overseas postings. In July 1940, the new
Chief of the Air Staff, Air Chief Marshal
Sir Charles Burnett, invited Bell to produce a proposal for a women's auxiliary under the supervision of her husband John, who had rejoined the Air Force at the war's outbreak and was now a
wing commander in the Directorate of Organisation at RAAF Headquarters,
Melbourne. Mary recommended forming the new service under the Air Force Act to permit women to enlist for the duration of the war under conditions similar to RAAF members, rather than enrolling on a short-term contractual basis, a radical idea at the time that would not be put in place until 1943. She also suggested a volunteer reserve or citizen force to augment the enlisted women, effectively the existing WATC, though this was seen as placing too much emphasis on her personal command. Some senior Air Force officers, including the recently promoted Air Marshal Williams, and the Director of Personal Services, Group Captain
Joe Hewitt, opposed a women's service. Burnett, an RAF member who appreciated how the WAAF proved its worth during the
Battle of Britain, championed its establishment as the
Women's Auxiliary Australian Air Force (WAAAF). Bell was appointed to the RAAF's Personnel Branch as Staff Officer (Administrative) with the probationary rank of
section officer (acting
flight officer) on 24 February 1941, to lay the groundwork for the new organisation. She was succeeded as Australian Commandant of the WATC by the
Countess of Bective, previously the State Commandant of South Australia. Formally established on 25 March, the WAAAF was the first uniformed women's branch of an armed service in Australia, predating
similar organisations in the Army and
Navy. Bell led the WAAAF for the first three months of its existence, recruiting approximately two hundred women by June; of the first six officers she appointed, five were former members of the WATC. The
Air Member for Personnel, Air Vice-Marshal
Henry Wrigley, chose Stevenson on the basis of her management background and because she was not a "socialite". Notwithstanding her aviation experience and familiarity with the RAAF, he considered Bell to be "tangled up with the WATC", where she "waved the flag and obtained a great deal of publicity for herself". Bell chose to resign on learning of Stevenson's appointment, rather than stay on and report to someone from outside the service fraternity; she later rejoined at Wrigley's request, but stipulated that she would accept no promotion higher than flight officer. Despite Bell's recommendation in July 1940 that women be enlisted into the WAAAF as permanent staff, they were at first enrolled only for renewable twelve-month contracts. They did not become part of the Permanent Air Force, with the benefits that entailed, until the Air Force (Women's Services) Regulations were enacted on 24 March 1943; that day, Bell's commission as a section officer, and her temporary rank of flight officer with effect from 1 October 1942, was promulgated in the
Commonwealth of Australia Gazette. Pay in the WAAAF was only ever two-thirds that of male equivalents. The organisation nevertheless grew rapidly, peaking in strength at over 18,600 members in October 1944, or twelve per cent of all RAAF personnel. ==Later life==