An unstable flight condition in which a rocket's spin causes the rear portion of the rocket to describe a circle. Coning greatly increases aerodynamic drag and reduces peak altitude.

Stability is often described in units of "Caliber" and a long, thin rocket with small fins may have several calibers of stability (because the Center of Gravity [CG] is well ahead of the Center of Pressure [CP]). But the small fins may not provide enough corrective force to overcome rotation around the CG until they are at a significant angle to the airstream. This slow reaction of the rocket to rotation around the CG causes coning.

A standard-shaped rocket will have the CG closer to the CP. Any rotation around the CG increases the Angle of Attack (and, therefore, the corrective force of the fins) more quickly than when the CG and CP are farther apart. This allows the rocket to react and correct its flight more quickly - eliminating the occurence of coning.