Each veteran that participates in the "Never Forgotten Honor Flight", gets the opportunity to witness one of the most symbolic ceremonies in Washington D.C., the changing of the guard at "The Tomb of the Unknowns" at Arlington National Cemetery.

The tomb represents every American soldier who died in a conflict, whose remains could not be identified.

The tomb is guarded 24 hours a day, 365 days a year by "Tomb Guard Sentinels". Only a small fraction of elite soldiers, with unblemished military records are even considered for the position.

Each soldier must be in peak physical condition and stand between 5'10" and 6'4".

There are 3 reliefs of guards, each having one commander and 6 sentinels. The reliefs are divided by height, so each guard during the change looks similar.

During the summer months, the tomb is guarded in half hour shifts and in the winter, the shifts last 1 hour.

During a shift, the guard walks back and forth in front of the tomb in a very calculated and meticulous manner.

The 21 gun salute is the highest honor a soldier can receive, therefore, the guard walks 21 steps in one direction, with his weapon on his opposite shoulder from the tomb.

On the 21st step, the guard stops and faces the tomb for 21 seconds. He then turns and faces the opposite way for another count of 21 seconds and then walks 21 steps to the other end of the tomb.

This process is repeated for the entire shift.

It's considered one of the highest honors to be selected to guard "The Tomb of the Unknowns".

Arlington National Cemetery holds more than 400,000 gravesites, containing the remains of servicemen from every major conflict, as well as government leaders and many presidents.