NYC Missile Defense system (2nd hand, no sauce)

Talked to an oldfag military vet today that I trust. He claims to have been stationed in NJ in the 1960's at a facility which had the primary purpose of the defense of NYC through use of ground-air missiles.

He claims that they, at the time, had the capability to track EVERY plane in the air in USA real-time and the capability to shoot them down. He said if 9/11 happened then, the first plane may have hit but there is no way in hell the 2nd would have even reached NY state line.

He cannot comprehend how 9/11 could have happened in the year 2001 when it would have been prevented in the 60's.