The preceding discussion shows that if  > M_cr, drag rises greatly. How can M_cr be increased?

1. Use a very thin airfoil with a sharp leading edge. This is impractical for airliners (where would fuel be stored?).
2. Reduce the curvature on the upper surface. This reduces the acceleration and deceleration of the flow, so that any shocks formed will be relatively weak.

Such airfoils were among the first to be designed using detailed mathematical computation.
 
 

Comparison of transonic flow over a "usual" (NACA 64A series) airfoil with transonic flow over a supercritical airfoil.