The little girl was deeply concerned.

So on Christmas Eve, she called in to the North American Aerospace Defense Command’s Santa tracking center with an urgent question:

“If I lose my tooth, and the Tooth Fairy comes, could the Tooth Fairy scare away Santa Claus?”

The Santa trackers at NORAD started on Christmas Eve at 6 a.m. ET, fielding questions from all over the globe and continuing a tradition that began by accident in 1955.

That year, an ad placed in a local Colorado Springs newspaper encouraged kids to call a phone number to find out Santa’s whereabouts on Christmas Eve, but instead of the intended number, the operations center for what is now called NORAD was printed.

Col. Harry Shoup was in charge that night, and instead of hanging up, he had his operators find Santa and report on his location.

NORAD is typically charged with detecting attacks against North America by aircraft, missiles or space vehicles, but on Christmas Eve, its high-tech tools of detection are repurposed to find and track Santa.

John Cornelio, a media spokesman at NORAD, says the organization is on track to receive more than 100,000 calls and 10,000 e-mails. He says the volunteer Santa trackers are mostly NORAD workers or their family members. After a quick briefing, the trackers start taking calls, relaying Santa’s position as shown on a big screen on the front wall of the call center. Tracking information is also posted to Facebook, Twitter and YouTube.

Cornelio says NORAD has learned that Santa “roughly arrives at homes between 9 p.m. and midnight, but only after the kids have gone to bed.” He says that kids can help make things a lot easier for Santa if they’re in bed at that time so he doesn’t have to backtrack.

As for the monumental logistical challenge of delivering all those gifts (NORAD reports that he’s already delivered more than 2 billion gifts, as of 1 p.m. ET), Cornelio says that time to Santa is different from what it is to most people.

“What seems like 24 hours to you and I actually is a lot more significant period of time to Santa. … That’s what allows him to actually travel all around the world in a 24-hour period.”

While the Santa trackers handle a variety of questions, there are some they just don’t have the answer to. One child called in earlier to ask if Santa likes President Barack Obama or his electoral opponent, former Massachusetts Gov. Mitt Romney. Cornelio replied: “Santa would have to best answer that question. What we do is make sure Santa travels safely.”