United 93 from Newark bound to San Fransisco, crashed in a field outside of Shanksville, PA. at 10:13 am after a scuffle between hijackers and passengers and crew. United 93 is the only hijacked flight that failed to reach it's intended target that day.
In the three days that followed the 9/11 terrorist attacks, when all commercial flights above the continental US were suddenly suspended, a veil was lifted on the profound, though until that point unconfirmed, effects that aviation-associated artificial clouds are having on our planetary environment.
In memory of the brave passengers of Flight 93: "In a field in Shanksville, PA, away from everything for miles around, people come from everywhere on Earth. Over 5,000 people, every week. To place a flag... to write a note... On anything available, including stones on the ground. 40 people heroically stopped an attack on America and saved many lives... LET'S ROLL..."