This is a visualisation of the cross-sectional profiles of 1,580+ aerofoils found in the UIUC Airfoil Coordinates Database, all relating to real lift-surfaces used by operational, experimental, and historical aircraft. In the visual above, the profiles are sorted by a close approximation of aerofoil thickness and overlayed. The raw data varies a lot in that there is little to no consistency in scale, proximity of leading-edge datapoints to the origin, rotation and so on, so each dataset had to be transformed for a more intuitive visual comparison. All transformations were made using MATLAB r2018a.

There are a few weird shapes in there: rotor blade ends, cowls, primitive Wright Brother aerofoil shapes; but predominantly there is an obvious popularity in the conventional symmetric tear-drop shape.