Monday's somber service began at 9:45 a.M., the time that federal investigators determined passengers decided to revolt against their four al-Qaeda hijackers, who ended up crashing the plane in a field 96 kilometers southeast of Pittsburgh.
The Republican said he was in Washington, as a member of Congress, on 9/11, and learned that the Capitol was a possible target of the hijacked plane, which was only 12 minutes away.
Thirty-three passengers and seven crew members were killed.
"Without regard to personal safety, they rushed forward to save lives," he said. "I will always believe that I and many others in our nation's capital were able to go home that day and hug our families because of the courage and sacrifice of the heroes of Flight 93."
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The day began with the tolling of bells and a reading of the victims' names, and remarks by Pennsylvania's Democratic Gov. Tom Wolf and US Secretary of the Interior Ryan Zinke.
Ground was broken Sunday on the final element of the Flight 93 National Memorial -- a 93-foot tall Tower of Voices. The tower, to be built near the park's entrance, will feature 40 tubular metal wind chimes, one each for the victims.
Bill Adderly, the father of flight attendant CeeCee Ross Lyles, said the Tower of Voices is an apt ending to the memorial site.
"We were here two days after the crash, and never in our imagination did we believe it would be this beautiful," said Adderly, of Fort Pierce, Florida. "The bells, the ringing, I could hear our daughter's voice in it. She loved to sing. She loved to praise the Lord."