Educated at Brisbane Grammar School, Don left without academic distinction to work on his father’s cattle station. His move to Brisbane and attendance as an evening science student at the University of Queensland, together with his rank as a non-commissioned officer in the Militia, resulted in a successful application to become a cadet in the Royal Australian Air Force. He joined on 16 July 1930 and began flying training at Point Cook, Victoria. At the end of the course he came second in the theoretical examinations and top in practical flying.
Through his acceptance of a short-service commission in the Royal Air Force on 11 August 1931, Bennett began an association with England; he was to live principally in the Home Counties for the rest of his life. He served with No.29 Squadron, flying the Siskin, a biplane fighter aircraft, and with No.210 Squadron, equipped with flying boats, before becoming an instructor. In January 1932 he had been promoted to flying officer. He left the RAF and transferred to the RAAF Reserve on 11 August 1935, holding a first-class civil navigator’s licence, a wireless operator’s licence, three categories of the ground engineer’s licence, a commercial pilot’s licence and a flying instructor’s certificate.
Bennett joined Imperial Airways Ltd in January 1936 and was soon flying between London, Paris and Cologne, Germany. Posted to Egypt, he flew Handley Page 42s to India and Kenya, and Empire flying boats from Southampton, England, to Alexandria and South African ports. In 1938 he published The Air Mariner, which was concerned with the handling of flying boats. That year Imperial Airways decided to fly the North Atlantic mail using a small four-engined aircraft, Mercury, launched from the back of a larger flying boat. Bennett was placed in command of Mercury and in July he successfully made the first commercial trans-Atlantic flight employing this revolutionary combination. In doing so, he achieved a record east to west crossing of the North Atlantic. For these feats he was awarded (1938) the Johnston memorial trophy and the Oswald Watt gold medal. In October he flew Mercury non-stop from Scotland to South Africa, setting a long-distance record for seaplanes. Next year he took part in proving the concept of air-to-air refuelling, designed to make possible non-stop trans-Atlantic commercial flights.
From July 1940 Bennett was flying superintendent of the Atlantic Ferry service, which was established to bring American aircraft to Britain. In mid-winter he personally led the first flight of seven Hudson aircraft to make the crossing. He rejoined the RAF on 25 September 1941 as an acting wing commander and became second-in-command of an elementary navigation school. In December he was given command of No.77 Squadron, which operated Whitley bombers; he consistently flew on operations. He became the commanding officer of No.10 Squadron, equipped with the Halifax bomber, in April 1942. Sent to attack the German battleship Tirpitz that month, his aircraft was shot down by ground fire over Norway. Bennett and several of his crew evaded capture and reached neutral Sweden. After release from internment, he returned to Britain and was awarded the Distinguished Service Order.
In July 1942, on promotion to acting group captain, Bennett was directed by Air Marshal Sir Arthur Harris to form and command the Pathfinder Force within Bomber Command. The establishment of a force to find and mark targets for night bombing raids was deemed essential if Bomber Command was to continue its offensive. Only one in three aircraft claiming to have attacked a target had got within five miles (8 km) of it. With a loss rate of between 4 and 5 per cent of the aircraft sent on each operation, Bomber Command was achieving very little at great cost. The appointment of Bennett with his superlative navigational skills and technical understanding was to be crucial to its success.
Harris later remarked that Bennett was the most efficient airman he had ever met. His Pathfinder Force, with its ability to guide bomber formations to their targets through the use of radar and pyrotechnics, greatly improved the accuracy and effectiveness of Bomber Command. Bennett saw the potential of the then underestimated Mosquito, and this magnificent aircraft, which could carry a 4000-lb. (1814 kg) bomb to Berlin, was used principally as the leading aircraft of Pathfinder marking forces. By May 1945 Bennett had eleven Mosquito squadrons. Frequently and against regulations he would fly a Mosquito himself to observe the marking of targets and the subsequent attacks.
In January 1943 the Pathfinder Force had become No.8 Group, Bomber Command, and Bennett had been promoted to acting air commodore. That year he was appointed CBE. In December he was promoted, at the age of 33, to acting air vice-marshal, becoming the youngest officer ever to hold such rank. Bennett was appointed CB and to the Russian Order of Alexander Nevsky in 1944. He was a fellow of the Royal Aeronautical and the Royal Meteorological societies.
The war had a sour ending for Bennett. Of all the senior RAF commanders he alone was not knighted. One explanation for such an omission lay in the reaction to his difficult personality. He possessed an impatient, dictatorial and pedantic style of command which, while sometimes most effective, inevitably made him enemies. Having had a strict Methodist upbringing, he never drank, smoked or was heard to swear and these strengths may have contributed to making him a difficult colleague in the masculine world of aviation. For example, he had left the Atlantic Ferry organisation after failing to reach amicable agreement with its executive, and during the war he had made an adversary of, among others, (Sir) Ralph Cochrane, who, when commanding No.5 Group, had become a rival in pioneering marking techniques for the main bomber forces. As Harris again said of Bennett: `He could not suffer fools gladly and by his own high standards there were many fools … Being still a young man he underrated experience and over-rated knowledge’. Bennett could be arrogant and abrasive. Yet many who served with him held him and his many skills in awe. His reputation for never asking anybody to do something he could not do himself was fully warranted.
Following the German surrender, Bennett was released by the RAF on 14 May 1945 so that he could contest a by-election for the House of Commons seat of Middlesbrough West as the Liberal Party candidate. He was elected unopposed, but was defeated at the general election in July and his brief period as a member of parliament ended with disillusionment and arguments. Bennett did not react sympathetically to party discipline. He stood unsuccessfully for North Croydon in 1948 and Norwich North in 1950.
Bennett had been appointed chief executive of the British South American Airways Corporation in 1945. He won his second Oswald Watt gold medal in 1946 for a survey flight to South America. His policy of using only British-made equipment, principally the Avro Tudor, and his conviction that the airline should return a profit, contributed to a series of tragic accidents. In 1948 the Tudor was grounded. Bennett publicly criticised the board of BSAA and was asked to retract his comments or resign. He refused to do either and was dismissed. During the Berlin airlift later that year he formed a profitable air transport company, Airflight Ltd, using two Tudors, which he later employed on equally profitable long-distance charter work as Fairflight Ltd until 1951. He then founded Fairthorpe Ltd, a company supplying sports cars in kit form, which he owned until 1983.
In 1958 Bennett published his memoirs, Pathfinder, a section of which resulted in a libel action. By the 1960s his political attitude had moved to the far right. He resigned from the Liberal Party in 1962 in opposition to its stand on the Common Market, and in 1967 stood as a National Party candidate in a by-election at Nuneaton, Warwickshire, and polled about five hundred votes. In 1969 he founded the Association of Political Independents, which had an aim of introducing a non-party parliament. He also gave support at times to the National Front and presided over the Independent Democratic Movement, which favoured the voluntary repatriation of immigrants. In 1970 he published a political tract, Let Us Try Democracy, which was critical of the then system of British government. Survived by his wife, and their daughter and son, he died on 15 September 1986 at Wexham Park Hospital, Slough, Berkshire, and was cremated. He is remembered as a superb aviator whose subsequent career was a disappointment.
On 21 August 1935 at the register office, Winchester, Hampshire, he married Elsa (`Ly’) Gubler. With her co-operation, he wrote The Complete Air Navigator (1935), which became the essential textbook on the subject and remained in print for over thirty years.