Nineteen years ago Friday, nearly 3,000 American lives were lost when planes were hijacked and flown into the World Trade Center in New York, the Pentagon just outside Washington, D.C., and into a field in Shanksville, Pennsylvania.
But as the U.S. commemorates that day of infamy, it is simultaneously grappling with the coronavirus.
Due to the pandemic, ceremonies that normally take place to commemorate this tragic day are starkly different this year.
In New York City, families of the victims of 9/11 and survivors have still been invited to the site of where their loved ones died, but they have been required to wear masks.
In prior years, names of those who died have been read aloud by family members and friends in the plaza. But this year, according to the National September 11 Memorial & Museum, the reading of those names has been pre-recorded to be played out on speakers.
Members of the general public have been discouraged to attend and pay tribute.
Vice President Mike Pence, former Vice President Joe Biden, New York Gov. Andrew Cuomo, former Mayor Mike Bloomberg and Sen. Chuck Schumer attended Friday's 9/11 Memorial & Museum official commemoration ceremony.
Pence broke away from the event to attend an alternate ceremony blocks away in Lower Manhattan, where the names of the dead were read in person by family members.
The alternate ceremony was organized by the Tunnel to Towers Foundation, and approximately 125 family members were in attendance.
The 9/11 Memorial and Museum will go ahead with its annual “Tribute in Light," beamed into the sky from its traditional location in Lower Manhattan, after initial plans to cancel the commemoration over coronavirus concerns were met with backlash. The lights will be turned on at sunset and will fade away at dawn Saturday.
The Pentagon held a ceremony at which Secretary of Defense Marker Esper and Chairman of the Joint Chiefs of Staff Mark Milley gave remarks. But the audience consisted solely of Defense Departments senior staff and officials. Family members of those who lost their lives were being allowed to visit later in the day but were not in the audience.
On Capitol Hill, Speaker Nancy Pelosi and other House members, wearing masks, gathered for a moment of silence on the steps of the U.S. Capitol at 8:46 a.m., then sang a verse of "God Bless America" as they memorably did the evening of the attacks.
As of Sept 1., 2020, 1,642 of the 2,753 victims of the attack on the World Trade Center have been positively identified, according to the NYC Office of the Chief Medical Examiner. 1,111 victims have not been positively identified, 19 years later.
More than 1,400 Sept. 11 survivors and responders have contracted the coronavirus so far, according to data from the World Trade Center Health Program.
Due to their compromised immune systems from surviving Sept. 11, especially their ailing respiratory symptoms, many have fallen ill. As of Aug. 21, at least 191 have been hospitalized and 44 have died.
John Feal, a former construction worker who has suffered long-term health damage from working at Ground Zero after 9/11, told ABC News that he remembers the nation’s unity after the attacks.
"If we were to bottle Sept. 12 and we learned to live like everyone did that day, the pandemic would go away a lot faster," Feal said.
ABC News' Ivan Pereira and Aaron Katersky contributed to this report.