Underwater vehicles traveling inside a bubble or supercavity enable the reduction of drag and increase of speed; however, planing forces generated when the vehicle aft end pierces the bubble can lead to oscillatory motion and instability. In this paper, a framework for the synthesis of planing avoidance controllers is presented and the trade-off between tracking performance and planing avoidance is investigated. We propose mathematical models of the supercavity and planing forces, based on experimental data, that are used to construct a nonlinear model of the vehicle dynamics and a simplified version suitable for analysis and controller synthesis. A planing metric, based on the simplified vehicle dynamics, is used within the controller synthesis to avoid planing. Simulations of vehicle maneuvers demonstrate that including planing avoidance as a control objective, reduces planing and increases the bounds of tracking commands for which the vehicle remains stable.