Re 'I understand ATC was introduced in the USA after the mid-air collision over the Grand Canyon in the 40s. Was it similar here in Australia?'
June 30th 1956 at around 10.30am, Two RPT aircraft flying virtually VFR, collided over the Grand Canyon.
United Airlines DC-7 v TWA L-1049 'Super Constellation'.
I think I have read where one of the aircraft was simply 'on track' whilst the other did a small diversion to enable the pax to enjoy the scenery of the Grand Canyon....
"The Board determines that the probable cause of this mid-air collision was that the pilots did not see each other in time to avoid the collision. It is not possible to determine why the pilots did not see each other, but the evidence suggests that it resulted from any one or a combination of the following factors: Intervening clouds reducing time for visual separation, visual limitations due to cockpit visibility, and preoccupation with normal cockpit duties, preoccupation with matters unrelated to cockpit duties such as attempting to provide the passengers with a more scenic view of the Grand Canyon area, physiological limits to human vision reducing the time opportunity to see and avoid the other aircraft, or insufficiency of en route air traffic advisory information due to inadequacy of facilities and lack of personnel in air traffic control."
Found it ....thanx to Google....