The process of analyzing hundreds of aircraft accidents has led to a five-factor model of the causes of pilot performance breakdowns. Obstacles to performance are one of the five major factors in the model. Seven major groupings of obstacles or obstructions to performance are identified. Each of the seven major groups are further delineated as to specific types of obstacles which may inhibit performance. These effects are discussed, along with suggestions for minimizing or removing the presence of the obstacles and obstructions.