The Schwarzschild and Kerr solutions have never properly explained the existence of powerful axial relativistic jets of materials ejected from black holes. A full solution for the velocity and radius at any distance from a black hole will be given for the Kinetic Spiral (KS) equation and axial event horizons are found at radii, r : = 3 √ ( M θ ± √ ( M θ 2 − α θ 3 ) ) , where Mθ = GM.sec2θ/ω2 and αθ = c2.sec2θ/3.ω2. It will be shown how the two trajectories of particles into a black hole can differ, either away from a black hole for relativistic jets or inward to accrete at the centre of a black hole. The mechanism for relativistic jets has been explained: at the gravitational radius, if the kinetic energy is... greater than or equal to the potential energy, then particles would receive a “relativistic gravitational slingshot” and be ejected in jets at relativistic speeds along axial event horizon lines. There are a number of jet parameters including velocity, Lorentz factor range, profile, collimation, type, luminosity, direction, mass ejection percentage, and observability that correspond to the KS model of relativistic jets. If the gravitational potential energy is greater than the kinetic energy at the gravitational radius, then particles will pass through the inner event horizon and be accreted at the centre of the black hole. A test of the KS theory has been given using data obtained from the recent observations of the size of event horizons of supermassive black hole Sgr A*, GW150914 and NGC 4486. The event horizons were found to be very close to the Schwarzschild radius, RS, at the outer event horizon, R+, in all three cases. These results provide strong support for KS theory. The outer event horizon of a black hole for KS was found to be at the Schwarzschild radius, R+ = RS. The inner event horizon of a black hole was found to be at 0.34 times the Schwarzschild radius, R- = 0.34 RS.