Russia's S-400 Air Defense System

Stealth designs have been built on low-detection by X-band radars, the most common military and civilian radars (others such as C-band – now known as the G/H band – are less prevalent). The F-35 has stealth protection mainly in the front of the aircraft, meaning that when it turns away from its target it is vulnerable. In time, the entire air defense system of the US and its allies, all based primarily on X band, will become obsolete as China and Russia move toward stealth aircraft and missiles.