The Saab 99 debuted in 1968 with all that plan view curvature. It was meant for aerodynamics, as was the sharply cutoff Kamm-style roofline of the notchback, and later, the coupe combi.
The 1967 (preproduction) Saab 99 notchback was 0.37 Cd, only matched by the Citroen DS (1955), and its distinctive curved windshield also helped significantly in reducing drag in side winds.*
You will notice that although the designers knew about flow detachment, as they had since Kamm's work, they did not go all the way in extending and/or extending the roof surfaces. The DS's flow detaches halfway back on the roof instead of where you'd expect at the rear window.
The Sonett III acheived 0.31 Cd according to my 1972 Saab brochure.
Saab lengthened and retrimmed the 99 into the 900 line in the late 70's- I have to imagine the aero only got better once they started adding air dams, flush headlights and flatter wheels. The 900 Aero and SPG (Sports PackaGe) trim levels added more goodies like side skirts and suspension upgrades.
*Source: "Saab 99 and 900: The Complete Story" by Lance Cole. In this 2007 printing the 99's aerodynamics are discussed on pages 38-39.
Like the 92-93-95-96 line, Saab by necessity made the basic 99 platform last for over 20 years. And the turbo's were still a blast to drive!
1968 Saab 99
Early 90's Saab 900 SPG
