Biden will travel Saturday to Shanksville, Pennsylvania, where United Flight 93 crashed in a field after passengers outgrew the hijackers and prevented another target from being hit.
Finally, the president will return to the Washington area to visit the Pentagon, the symbol of US military power that was crossed by another of the planes that were used as missiles that day.
The anniversary comes shortly after the end of the US-led war in Afghanistan, launched some 20 years ago to eradicate al Qaeda, which carried out the 9/11 attacks.
The Biden-ordered withdrawal of US troops in August, months after the deadline set by his Republican predecessor, Donald Trump, and the country’s resulting rapid fall to the Taliban has drawn criticism from members of both political parties.
Biden is not scheduled to comment on either site, but he released a video on Friday to express his condolences to the victims’ loved ones and highlight the national unity that resulted, at least initially, after 9/11.
“It’s so difficult. Whether it’s the first year or the 20th, children have grown up without parents and parents have suffered without children,” Biden said.
The president highlighted the heroism seen in the days after the attacks.
“We also saw something too rare: a true sense of national unity,” Biden said.
Biden, a Democrat, vowed to build that unity after he took office earlier this year, but the country remains deeply divided politically.
American presidents often travel to one of the three attack sites on the 9/11 anniversary, but it is unusual to go to all three on the same day.
“The president felt it was important to visit each of these three sites to commemorate the lives lost, the sacrifices made in one day that has impacted millions of people across the country, but certainly many people in those communities,” said the Friday White House spokeswoman Jen Psaki.