Against the backdrop of the latest news about the S-300 and S-400 air defense systems, this can also be said about the MIM-104 Patriot air defense system; we are publishing data on the effectiveness of these systems in defeating ballistic missiles. Let's start with the fact that 100% air defense is not yet in the world; it is wrong to judge the effectiveness of air defense systems by the effectiveness of intercepting ballistic missiles. The main function of the S-300, S-400 and Patriot air defense systems is to defeat aerodynamic targets flying horizontally, such as airplanes, helicopters, cruise missiles and large UAVs. It is worth noting that in order to intercept cruise missiles, the air defense system must have a radar to detect low-flying targets; in practice, this is not always the case. The defeat of ballistic missiles is a secondary function of these and air defense systems of this class developed in other countries. A ballistic missile is a difficult target; the Russian Iskander ballistic missile reaches speeds of up to 7,300 km/h in the final phase of its flight, and the American ATACMS missile reaches 3,700 km/h. The difficulty of defeating ballistic missiles is that the missiles develop high speed and approach the target from above, air defense crews do not always have time to detect them, and there is little time left to hit the target. It is also worth noting that the radars of modern air defense systems do not work all the time, since they have their own resource. There is little data on hitting ballistic targets, but it is known. The probability of intercepting a ballistic missile from the Patriot PAC-3 air defense system is from 60 to 80%, provided that there is no interference and the target is not maneuvering. The S-300 air defense system is capable of hitting a ballistic missile with a probability of 50 to 65%. The S-400 air defense system is capable of hitting a ballistic missile with a probability of no higher than 80%, also in ideal conditions. Thus, it is incorrect to judge the effectiveness of current air defense systems based on their capabilities.