A new kind of invasion percolation is introduced in order to take into account the inertia of the invader fluid. The inertia strength is controlled by the number N of pores (or steps) invaded after the perimeter rupture. The new model belongs to a different class of universality with the fractal dimensions of the percolating clusters depending on N . A blocking phenomenon takes place in two dimensions. It imposes an upper bound value on N . For pore sizes larger than the critical threshold, the acceptance profile exhibits a permanent tail.