The SAM Installation is the most powerful anti-air defense a Nation can build but it requires the Information Age. This defense turret engages hostile aircraft by firing salvos of 3 radar-guided missiles at it. These are very deadly, especially against primitive aircraft.
However it dosen't prove much of a threat to ground units and can be razed by hostile forces. Also, Stealth Bombers can bypass these undetected and wreck havoc on buildings. Moreover, enemy Special Forces units can jam your SAM installations, making them obsolete until those scouts move or are eliminated. Otherwise, they are deadly to anything else in the skies.
SAM installations should be well protected by ground forces and Advanced Fighters should be on hand when enemy Stealth Bombers are deployed.