U.S. First Lady Michelle Obama on Saturday participated in a memorial ceremony in honor of the passengers and crew of United Flight 93 in Shanksville, Pennsylvania.

In remarks delivered at the ceremony, Michelle Obama praised the United Flight 93 passengers’ valor.

The flight was en route from Newark, New Jersey to San Francisco on Sept. 11, 2001, when hijackers seized control and intended to attack Washington D.C.. But the 40 passengers on the plane fought back and the hijackers responded by crashing the plane about 100 kilometers southwest of Pittsburgh.

“They rose as one, they acted as one, and together, they changed history’s course,” said Michelle Obama, noting that “they remind us — not just by how they gave their lives, but by how they lived their lives — that being a hero is not just a matter of fate, it’s a matter of choice.”

Michelle Obama visited the site with her predecessor, Laura Bush. President Barack Obama on Saturday participated in a memorial ceremony on the grounds of the Defense Department’s headquarters, where a hijacked plane slammed into the Pentagon, killing 184 people on Sept. 11, 2001.