As Santa delivers billions of presents to little boys and girls around the world, personnel at North American Aerospace Defense Command are once again tracking his every move.

For the 57th straight year, NORAD headquarters in Colorado Springs, Colo. will be a hub of activity as radar, satellites, Santa Cams and even fighter jets follow Santa and his reindeer on their worldwide adventure.

“Amazingly, Rudolph's bright red nose gives off an infrared signature, which allows our satellites to detect Rudolph and Santa,” the agency says on its website.

Canadian pilots flying CF-18 fighter jets will greet Santa when he arrives in North American airspace, while American fighter pilots get to escort Santa as he flies through U.S. skies.

Defence Minister Peter MacKay announced Monday that Lieut.-Col. Daniel McLeod, Cpt. Shamus Allen, Maj. Benoit Bouchard and Cpt. Vincent Landry have been selected to escort Santa through Canadian airspace.

"For more than 50 years, our fighter jets have tracked Santa as he enters Canadian airspace and have provided an escort from coast to coast to coast to the jolly old man as he visits the homes of our fellow Canadians,” MacKay said in a statement.

MacKay added that the pilots “will be armed with cookies and milk.”

NORAD will be updating Santa’s progress on its Santa-tracker website, and via its Facebook page and Twitter account @NoradSanta.

By late Monday night, Santa had delivered close to 5 billion presents.

Santa usually starts his Christmas journey in the South Pacific, before making his way to New Zealand, Australia, Japan, and across Asia and Africa before heading to western Europe and then North America.

But, as NORAD points out, “Santa’s route can be affected by weather, so it’s really unpredictable.”

The annual tradition began in 1955, when an ad by Colorado Spring-based Sears Roebuck & Co. printed the incorrect phone number for children to call Santa. Rather than reaching the North Pole, children who dialled the number reached NORAD’s predecessor agency, CONAD (the Continental Air Defense Command).

The director of operations at the time, Col. Harry Shoup, directed staff to monitor Santa’s progress via radar, and to update any children that called through.

When NORAD was created in 1958, the agency carried on the tradition.

“Each and every day throughout the year, all of us here at NORAD work diligently to defend and protect our nations,” NORAD commander Gen. Charles H. Jacoby, Jr. said in a statement.

“It is an honour for us to take one day each year to expand our missions to share goodwill and holiday spirit across the globe through the NORAD Tracks Santa program. We owe all of this to Colonel Shoup, whose good humor in responding to that first call so long ago began our Santa-tracking tradition, and we're proud to carry this mission along to this day.”

Volunteers will spend Christmas Eve answering phone calls and emails from kids. They began taking calls at around 4 a.m. Mountain time Monday and will continue until 3 a.m. Christmas Day.

About nine hours into the operation, NORAD announced that it had fielded more than 24,000 calls from children asking questions ranging from Santa’s age to when the big man might be coming down their chimney.

One 10-year-old was concerned that Santa wouldn’t find him because he had yet to decide whether he would be sleeping at his mom’s or his dad’s house.

“I told him Santa would know where he was and not to worry,” said volunteer Glenn Barr.

Another child wanted to know if Santa is real.

Air Force Maj. Jamie Humphries took the call. He said, “I’m 37 years old and I believe in Santa, and if you believe in him as well, then he must be real.”

The child then hollered to his family: “I told you guys he was real!”

With files from The Associated Press