These aircraft were designed for QANTAS but by 1939, some had been sold to other civilian airlines.
In 1939, all civilian aircraft were impressed into RAAF service.

From the Australian War Memorial official website:

A De ...

These aircraft were designed for QANTAS but by 1939, some had been sold to other civilian airlines.
In 1939, all civilian aircraft were impressed into RAAF service.

From the Australian War Memorial official website:

A De Havilland DH 86A air ambulance (A31-7), one of eight used by the RAAF from 1939 until 1945. Capable of carrying one doctor and up to eight patients, (six of whom can be carried on stretchers), these four engined biplanes served with 35 and 36 Squadrons and 1 Air Ambulance Unit (1 AAU).
A31-7 served with 1 AAU in the Middle East. It arrived at Cairo on 3 July 1941 and was based at Gaza and Gerawla supporting the work of 1 Australian General Hospital before being damaged on the ground in an enemy attack on Mersa Matruh airfield on 31 January 1942.
Despite being riddled with shrapnel holes, it was repaired with parts scavenged from enemy aircraft and flown again, being the only aircraft 1 AAU had which was capable of flying for most of the first half of 1942.
As the last operational DH 86A, A31-7 was withdrawn from use due to the unavailability of 77-octane fuel after transporting patients during the Italian campaign in 1943. It has been suggested that the aircraft was then dismantled for spares and probably scrapped.
A total of 8,252 patients were airlifted by 1 AAU during the unit's service in the Middle East and Italy.

RAAF DH86A