[en] A kinetic ballooning mode theory is developed from the gyrokinetic equation in the frequency range for which the ions are fluid, the thermal electron response is adiabatic and the hot electrons are non-interacting due to their large drift velocity. Trapped particle effects are ignored, The application of the quasineutrality condition together with the parallel and binomial components of Ampere's Law reduces the gyrokinetic equation to a second order ordinary differential equation along the equilibrium magnetic field lines. The instability dynamics are dominated by the pressure gradients of the thermal species in the fluid magnetohydrodynamic limit. The resulting equation combines features of both the Kruskal-Oberman energy principle and the rigid hot particle energy principle proposed by Johnson et al. to model the Astron device