Millions of Americans are remembering the nearly 3,000 lives lost on 16 years ago in the September 11 terror attacks.

Hijackers flew commercial airplanes into New York's World Trade Center, the Pentagon and a field near Shanksville, Pennsylvania on September 11, 2001.

The National Fallen Firefighters Foundation hosted the annual Memorial Stair Climb at the Sunsphere. Each participant will pay tribute to a New York first responder who died in the attacks by climbing the equivalent of the 110 stories of the World Trade Center. Each participant also carried the name of one of the victims.

Hundreds of bikers hit the road Sunday in honor of the nearly 3,000 lives lost. A ceremony took place at World's Fair Park in the morning and the bikers followed along the remembrance ride route. The journey ended at the Bootlegger's Harley Davidson on Lovell Road. Each biker paid a $20 entry fee which went to Blount County Rescue, Seymour Fire Department, and Fallen Officer groups in East Tennessee.

A group of UT Knoxville students also decided to pay tribute to the victims of 9/11 on Sunday. Several students gathered near the Humanities building to plant American flags in their honor. The group wanted to show the importance of that day to students who may not even remember it.

President Donald Trump and first lady Melania Trump presided over his first 9/11 commemoration in his office on Monday.