Ballooning flute modes in tokamaks in the presence of trapped high energy particles are investigated. It is shown that a stability window occurs when a finite population of high energy particles exists. In appropriate conditions, high energy particles may lead to stable values of pressure that are considerably higher than those predicted by ideal MHD theory. It is found that the stability window is very sensitive to the main plasma component parameters and to the value of the hot particle pressure. It is shown that perturbations with characteristic frequencies ω* and D are increased out of the stability region; here, ω* is the ion drift frequency and D is the average magnetic drift frequency. The corresponding growth rates and threshold conditions are obtained.