NORAD defends North American air space from attack: the North American Air Defence Command.
Click this link to NORAD's site. The photo is revealing. Look to the left of the gentleman who is staring at the RADAR screen. It looks like a PC-AT, 1985 vinttage. Do you think it's y2k-compliant?
Warning: in the time it takes to download this photo, a nuclear missile launched from 200 miles off shore could wipe out Los Angeles. Maybe 2000 miles.