In 1948, Strang and his wife, Margaret, moved to Melbourne, Australia to work at the Aircraft Research Laboratory (ARL).
In 1955, he was appointed Chief Designer of Bristol Britannia, which was a large aircraft intended for transatlantic service.
In 1956, when the STAC (Supersonic Transport Aircraft Committee) was formed, Strang was a significant force in forming a final conclusion of the feasibility to build a supersonic transport of slender delta-wing platform with aerodynamics based on the separated flow principle developed by Dietrich Kuchemann and others at the Royal Aircraft Establishment during 1950–54.
The Filton team was given partial funding to explore the possibility of creating an aircraft capable of carrying 130 passengers for 3,000 miles (4,800 km) at Mach 2.2, in collaboration with France and/or the United States of America (USA).
Filton had already secured a contract for an all-steel supersonic research aircraft, known as the Type 188, which first flew in April 1962.
This experience convinced the team that civil supersonic transport should be limited to a speed consistent with the use of aluminum alloys.
Strang's earlier research into supersonic flow in Australia was ideal preparation for this work and provided invaluable expertise and management experience for the new tasks related to Concorde.
In the same year, Strang, together with (Sir) Archibald Russell and Mick Wilde, became involved in discussions with representatives from Sud Aviation, the French aerospace company based in Toulouse, France.
By the end of 1961, French and British governments were ready to direct BAC and Sud Aviation to formulate a joint project.
These studies, concluded in January 1962, that it was possible to have two aircraft designs with a great degree of commonality in research and development tests, structural components, jigs and tools, and engines.
The four men most closely concerned with the joint design discussions were, on the British side, Dr. A. E. Russell (later Sir Archibald Russell), Technical Director of BAC's Filton Division, and Dr. W. J. Strang (Bill Strang), Chief Engineer of Filton Division, and, on the French side, Pierre Satre and Lucien Servanty, Technical Director and Chief Engineer respectively of Sud-Aviation.
They were, one might have thought, a fairly unlikely pair to work together as collaborators on the most difficult technological project ever tackled in Europe.
Yet this partnership, like many others in the Concorde organization, grew and flourished on the firm basis of mutual respect for the each other's intellect and integrity.
At the end of the year, Dr Russell, the original inspiration behind the project (and the one who had persuaded Bill Strang to return from his research in Australia) retired.
In December, Concorde 01, ordered at the end of 1969, made its first flight from Filton to Fairford, a very good achievement by Bill Strang and his colleagues.