Survivors fleeing, covered in debris. First responders hoisting the American flag over rubble. The New York skyline filled with ash — its two twin towers newly missing. Seventeen years after the Sept. 11 terrorist attacks, these are the images that are still etched in Americans’ minds. Nearly 3,000 people died on Sept. 11, 2001, making it the deadliest terrorist attack on U.S. soil.

Remembrance ceremonies will mark the anniversary across the country on Tuesday, including the site of the crashes in New York, Washington and Pennsylvania. President Trump and first lady Melania Trump will attend a remembrance in Shanksville, Pa.

As President George W. Bush said in his November 2001 address to the United Nations: “Time is passing. Yet, for the United States of America, there will be no forgetting September the 11th.”

Listen to the story about Heather Penney, an F-16 fighter pilot whose mission was to bring down the fourth hijacked plane on 9/11:

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