Small fencelike surfaces extending in front of the wing and attached to the undersurface. They are particularly useful in preventing span-wise flow at high angles of attack, by shedding a vortex, similar to that of a wing fence. It is for this reason that they are located close to the stagnation line. The vortilons generate a vortex over the upper surface at high angles of attack, when most needed. Engine mounting pylons can conveniently be used for the same purpose.