The past weekend was filled with honor for 9/11 victims across the U.S. -- and some jitters as well.
On Sunday, F-16 military jets escorted a Frontier Airlines plane to Detroit after the crew reported two people spending a long time inside a bathroom.
Fighter jets also accompanied an American Airlines plane to Kennedy Airport after the crew reported some passengers going to the bathroom again and again.
In both cases, authorities released the suspects after questioning.
"That's a little unnerving," passenger Lisa McCann said. "I'm glad I didn't know it at the time. I think we were all a bit nervous about flying on 9/11."
In yet another security scare, authorities closed part of the Kansas City airport after finding suspicious items in a carry-on bag. Investigators later determined the bag contained no explosives.
"This is the craziest day we've ever had here," one TSA agent told The Wichita Eagle.
In New York and Washington, D.C., stepped up security was obvious over the weekend. ABC News reported the high security level will continue for at least another day as authorities investigate a threat from al Qaeda.
At memorials throughout the day, four separate moments of silence marked the exact moments when individual commercial airliners hit the World Trade Center towers, the Pentagon and crashed into a Pennsylvania field.
Families of the victims got their first look at New York City' new Ground Zero memorial - and remembered their loved ones 10 years later.
"I wish my dad had been there to teach me how to drive, how to ask a girl on a date," said Peter Negron, whose father died at the World Trade Center when he was only 11 years old.
"I hope that I can make my dad proud of the young men my brother and I have become," he added. "I miss you so much, Dad."
Country music recording artist Alan Jackson performed at a memorial service held at the National Cathedral, and President Obama also spoke at a Concert for Hope at the Kennedy Center.
"Decades from now, Americans will visit the memorials to those who were lost on 9/11, and they will know that nothing can break the will of a truly United States of America," the president said.
Before dawn Sunday, two columns of light filled the space where the Trade Center towers once stood, reminding all of the enduring tragedy - and America's resolve to never forget.