PETERSON AIR FORCE BASE, Colo. – Tens of thousands of children call NORAD on Christmas Eve eager to hear how far Santa is from their town, but the volunteers answering the phones have a welcome bit of news for parents, too: St. Nick won’t stop at homes unless all the kids are asleep.

Volunteer Liz Anderson said that when she tells kids that, she will sometimes hear parents say, “See! I told you.”

Tracking Santa’s travels, a celebrated tradition at the North American Aerospace Defense Command, unfolded Friday for the 55th year.

It takes four months of planning to marshal the 1,200 volunteers, 100 telephones, 30 laptops and two big projection TV screens the exercise requires, NORAD spokeswoman Joyce Frankovis said. All the labor is volunteer. Google, Verizon, Air Canada, defense contractor Booz Allen Hamilton and others chip in.

“It is tremendously fun,” said Jim Jenista, NORAD’s deputy chief for joint training exercises.

NORAD Tracks Santa, the official name of the exercise, began in 1955 when a Colorado Springs newspaper ad invited kids to talk to Santa on a hotline. The phone number had a typo, and dozens of kids dialed the Continental Aerospace Defense Command in Colorado Springs, NORAD’s predecessor.

The officers on duty played along and began passing along reports on Santa’s progress. It’s now a cherished ritual at NORAD, a joint U.S.-Canada command that monitors the North American skies and seas from Peterson Air Force Base in Colorado Springs.

Last year, volunteers answered 74,000 phone calls and 3,500 e-mails from around the world last year.

“It’s really ingrained in the NORAD psyche and culture,” said Canadian Forces Lt. Gen. Marcel Duval, the deputy commander of NORAD. “It’s a goodwill gesture from all of us, on our time off, to all the kids on the planet.” Volunteers answer calls in two-hour shifts from 2 a.m. Mountain Time on Christmas Eve until 3 a.m. Christmas Day.