North American Aerospace Defense Command (NORAD) provides aerospace warning and defense for Northern America.
But most don't pay attention to NORAD because of that - the missile defense system is known for tracking Santa's sleigh as he delivers gifts around the world.
The tradition of NORAD tracking Santa's Christmas Eve travels started with an innocent accident in 1955. Sears Roebuck & Co published a "call and talk to Santa" phone number that was one digit off from the air missile defense system.
Air Force Col. Harry Shoup got the phone call at his office. This was not a normal phone line but a top secret line that would ring if the Russians were attacking.
A tiny voice asked, "Is this Santa Claus?"
"Dad's pretty annoyed," said Terri Van Keuren, Shoup's daughter. "He barks into the phone," demanding to know who's calling.
"The little voice is now crying," Van Keuren continued. "'Is this one of Santa's elves, then?'"
Before long, the phone was ringing off the hook, and, softening up, Shoup grabbed a nearby airman and told him to answer the calls and, Van Keuren said, "'just pretend you're Santa.'"
To quote the official NORAD Santa site, "a tradition was born."