1960's have been a time of explosive growth in air travel around the world. The number of aircraft grew steadily, which affected flight safety. The only way to reduce the number of air transport was to increase its passenger capacity.
The pioneers of the new milestones in the aircraft industry were the Americans. At the end of the 70, the world saw the huge double-deck Boeing-747 liner, which is still popular today.
The USSR in this sense was catching up. First KB them. Ilyushin planned to create a new flagship of civil aviation based on the already used IL-62, about which we told earlier. However, later the designers came to the conclusion that the elongation of the fuselage significantly reduced the flight characteristics of the future aircraft.
It became clear that the need to increase the passenger capacity is not due to elongation, and the expansion of the fuselage.