Until some time into WW2 no aircraft had even been flown as a matter of course (compared to the pioneers) across the Atlantic. They were all crated and shipped as deck cargo. The quite substantial fleets of late 1930s DC2 and DC3 which a number of European airlines took were all built in California, flown to the East Coast, dismantled, shipped as deck cargo to Amsterdam, and reassembled by Fokker.
A photo from the 1970s showed a Soviet freighter with an Ilyushin 14 twin-prop piston (about the size of a Convair 240) loaded (uncrated, not even tarpaulined) as deck cargo, wings lashed alongside the fuselage, travelling to Antarctica to support the Soviet base there. It's a straightforward operation. Probably getting the parts to/from an airfield is the difficult bit.
Australia from the UK is somewhat easier, under normal circumstances the longest overwater stretch is only about 400 miles from Indonesia to Darwin across the Sea of Timor. Once Europe was invaded in 1940 there was the need to fly round over the Bay of Biscay and through North Africa, then when Japan invaded Asia at the end of 1941 that broke the air route other than the few but well-known "double sunrise" Catalina operations from Colombo direct to Perth. The invasion happened sufficiently quickly that a number of both Imperial Airways and Qantas Empire flying boats were trapped on the "wrong" side of the divide, and the aircraft were thus exchanged between the two companies.
De Havilland of course established a substantial manufacturing facility in Australia, that initially built Hatfield designs, and later went on to develop some of their own. They did the same in Canada.
Last edited by WHBM; 29th Dec 2017 at 10:33.