A graduate of RAAF College, he began his career flying CAC Sabre jet fighters in Australia and South East Asia in the 1950s and 1960s.
[7] In 1971 he became the first RAAF officer to attend the US Air War College, and received a master's degree in political science from Auburn University.
On 8/9 April 1974, Funnell flew an F-111 around Australia to commemorate the 1924 circumnavigation of the continent by Wing Commander Stanley Goble and Flight Lieutenant Ivor McIntyre in a Fairey III seaplane.
[11][12] Promoted to air commodore, Funnell was appointed Chief of Staff at Headquarters Operational Command in Glenbrook, New South Wales, in 1979.
[1][19] The Air Power Manual, the RAAF's first self-produced treatise on aerial war fighting, was completed by a development team sponsored by Funnell, and published in 1990.
[21][22] As CAS, Funnell focused on turning the RAAF into the "air power element of a cohesive, integrated defence force".
[24][25] The Air Force was in the process of re-equipping its Mirage III fighter squadrons with the F/A-18 Hornet when Funnell became CAS, and he had to contend with a shortage of pilots that was exacerbated by the extra training time required for the new aircraft.
[26][27] In September 1988, he flew one of the RAAF's recently acquired Pilatus PC-9 turboprop trainers in the Bicentenary Round Australia Air Race.
[3][28] His term coincided with the 1990–91 Gulf War;[29] the RAAF's contribution included transporting Australian hostages and medical staff from the Middle East.
[30][31] Funnell was appointed a Companion of the Order of Australia (AC) on 12 June 1989 for his service as CAS, and awarded the US Commander of the Legion of Merit in 1991.
[7][33] Funnell's five-year term as CAS was the longest since that of Air Marshal George Jones, who served ten years in the post from 1942 to 1952.
[37] He publicly disavowed the Australian contribution to the 2003 invasion of Iraq but, once battle was joined, opposed the withdrawal of troops and cautioned against anti-war demonstrations.