The Royal Air Force began developing an airfield at Butterworth, in what was then Province Wellesley, in 1939, on a care-and-maintenance basis, and opened it as RAF Station Butterworth only in October 1941. Hugh Crowther’s history for the RAAF Association is blunt about what followed: the station "was ill-prepared when Japan attacked the base in December 1941."

According to Wikipedia’s account of the Malayan campaign, Ki-21 bombers of the 7th Hikodan struck Alor Star, Sungai Petani and Butterworth on the first day of the invasion, part of a day on which some 60 Allied aircraft were lost, most of them on the ground. No. 62 Squadron’s Blenheims had moved to Butterworth from Alor Star and were moved on to Taiping on 10 December. The airfield was captured by units of the Japanese 25th Army on 20 December 1941 and stayed in Japanese hands until September 1945.

The RAF came back after the war and resumed flying in May 1946. From 1950 Butterworth was one of the Far East Air Force’s stations in the Malayan Emergency, and Wikipedia lists the armament practice camps and squadrons that used it, from Venoms to Bloodhound missiles.

In 1957 the RAF closed the station and transferred the airfield to Australia. The RAAF took formal control on 30 June 1958, and Butterworth became, in the RAAF’s own words on its base page, the only permanent major air base it has operated outside Australia. No. 2 Squadron’s Canberras arrived in July 1958 and, according to Wikipedia, flew formation bombing runs against guerrilla targets almost at once; they stayed until 1967, when the squadron moved to Phan Rang in South Vietnam.

The base reshaped Butterworth and Penang. Malay Mail reported in 2015 that Australian personnel and dependants peaked at nearly 5,000 in the 1970s, living across the island in Tanjung Bungah, Tanjung Tokong and Batu Ferringhi; the base ran a hospital that also served local people, and Radio RAAF Butterworth’s Saturday-night dedication programme introduced a generation of Penangites to Western pop music. Wikipedia records an RAAF school in Penang opened on 9 May 1962, whose enrolment peaked at about 1,100 in 1977.

Wikipedia says control of the base passed to the Royal Malaysian Air Force in 1970 and the property was ceded to the Malaysian government, but the Australian presence was still large: the schools closed only in 1987 and 1988, as the last fighters left.

Australian fighters arrived with the Canberras. No. 3 Squadron flew CA-27 Sabres from Butterworth from 1958, and with No. 77 Squadron it took part in the last years of the Emergency and in Konfrontasi. From August 1964, according to Wikipedia, the two squadrons scrambled several times when Indonesian Air Force MiG-21s approached Malaysian airspace; the Indonesian aircraft always turned back before crossing the boundary, and no engagement is recorded.

The Mirage IIIO replaced the Sabre in two steps. No. 75 Squadron arrived on 18 May 1967 and No. 3 Squadron, re-equipped at Williamtown, came back in February 1969, when No. 77 Squadron went home. The Mirages also flew detachments to Tengah and Paya Lebar in Singapore. No. 75 Squadron withdrew to Darwin in October 1983 and No. 3 Squadron left in 1986 to become the RAAF’s first Hornet squadron; what remained became No. 79 Squadron, whose departure in May 1988 ended thirty years of Australian fighters at Butterworth.

When the Five Power Defence Arrangements took effect in 1971, Butterworth became the seat of the Integrated Air Defence System, the joint command for the air defence of Malaysia and Singapore. Wikipedia notes that the headquarters was renamed the Integrated Area Defence System in 2001, now draws on all three services of the five nations, and is commanded by an Australian air vice-marshal; the United Kingdom’s contribution to the staff is five officers and NCOs.

The headquarters coordinates the annual exercises, Bersama Shield and Bersama Lima, which bring dozens of aircraft and ships together. In September 2019 six Typhoons of the RAF’s II(AC) Squadron and more than 200 personnel flew to Butterworth for Bersama Lima 19, supported by a Voyager tanker. The RAAF keeps No. 19 Squadron and No. 92 Wing’s Detachment A here, and the Australian Army a rifle company and training group.

For the RMAF, Butterworth is the northern fighter base. Eight F/A-18D Hornets, all two-seaters, were delivered between March and August 1997 and went to No. 18 Squadron here; three of them took part in the opening strikes at Lahad Datu in Sabah on 5 March 2013. Wikipedia also places No. 15 Squadron’s Hawks and No. 3 Squadron’s leased AW139 helicopters at the base.

The fleet is small and ageing. One Hornet was lost after an engine fire on 21 August 2025, and a plan to add Kuwait’s retired F/A-18C/Ds was cancelled in February 2026, which leaves the KAI FA-50M, ordered in 2023, as the next new jet. The AIP gives the airfield a single 2,438 m runway, 18/36, with prior permission required for every non-military aircraft.