COLORADO SPRINGS, Colo. -

It's the busiest travel day of the year, for Santa of course!

As usual, NORAD keeps track of Santa's flight.  At their headquarters in Colorado Springs, volunteers updated kids on his progress through thousands of phone calls, emails and on twitter.  NORAD also kept their website up-to-date with Santa's progress.

They estimate receiving about 3,700 phone calls per hour.  A volunteer staff of 1,250 answered phones on two-hour shifts for 24 hours.

For the third year in a row, First Lady Michelle Obama answered phone calls from kids.

"This is such a wonderful holiday tradition, and I'm always so thrilled to be a part of it.  I love hearing the excitement and anticipation in the children's voices as they learn Santa's location ... that's what brings the magic of this night to life for all of us," said Mrs. Obama.

From NORAD:

"The tradition began in 1955 after a Colorado Springs-based Sears Roebuck & Co. advertisement misprinted the telephone number for children to call Santa. Instead of reaching Santa, the phone number put kids through to the CONAD Commander-in-Chief's operations "hotline." The Director of Operations at the time, Colonel Harry Shoup, had his staff check the radar for indications of Santa making his way south from the North Pole. Children who called were given updates on his location, and a tradition was born."

In 1958, the governments of Canada and the United States created a bi-national air defense command for North America called the North American Aerospace Defense Command, also known as NORAD, which then took on the tradition of tracking Santa.

NORAD uses four high-tech systems to track Santa – radar, satellites, Santa Cams and fighter jets.