Fifteen years on, a generation of Americans who have no firsthand memories of the Sept. 11, 2001, terrorist attacks are starting to come of age. That realization weighed on the filmmakers behind “9/11” as they prepared the 15th anniversary edition of the extraordinary documentary that features the only video footage shot inside the World Trade Center on that devastating morning.

The backstory of “9/11” is well-known by now: French filmmakers Jules and Gédéon Naudet and firefighter/director James Hanlon were filming a documentary about a rookie firefighter when they found themselves bearing witness to history. Jules Naudet caught footage of the first plane hitting Tower 1, and he followed firefighters inside the building as the frantic rescue effort began. His camera kept rolling even as the skyscraper collapsed.

The Naudet brothers and Hanlon have produced updated material for “9/11” every five years. As work on the 15th anniversary edition began, the trio decided it was time to ensure the movie would be preserved and properly showcased for generations to come. They cut a deal for CNN to acquire all rights to the film and all of the raw footage they collected on Sept. 11 and the days that followed. CNN plans to build a digital archive for “9/11” material that will allow users to access roughly 100 hours of footage, the vast majority of it unseen.

“We often talk to high school students, and one of the more fascinating things about the kids who were either too young or not born [on Sept. 11] is that they are such a visual generation,” Jules Naudet says. “The film resonates so much more with them. They can put themselves in that place.”

CNN will air “9/11: Fifteen Years Later” twice starting at 8 p.m. on Sept. 11. A limited amount of new material will be available on the CNN Films website, but the archive will take time to build out. For starters, they have to digitize and preserve all of the master tapes.

TV Tributes
Among the special programming slated to mark the 15th anniversary of the 9/11 attacks:
“Ground Zero Rising: Freedom vs. Fear”
An hour-long look at the revitalization of the World Trade Center site
“America’s 9/11 Flag: Rise From the Ashes”
Details the disappearance of the flag raised in the WTC rubble by three firefighters
“9/11/01: The Today Show”
A three-hour rerun of the NBC show that day
Fox News
“9/11: Timeline of Terror”
Draws from the network’s archives to re-create the timeline of events
Smithsonian Channel
“9/11: Day That Changed the World”
Revisits the actions of leaders including President George W. Bush

“This is not going to be just a dump of raw footage,” says Amy Entelis, CNN’s exec VP of talent and content development. “There is a big opportunity for us to organize the material in different ways and make interactive features. We want to make it into a resource not just for us but for people who are studying these events.”

For the Naudets and Hanlon, reviewing the movie periodically reminds them of the global repercussions of the attacks on New York and the Pentagon, as well as the plane that went down in Pennsylvania. The attacks left nearly 3,000 dead, including 343 members of the New York City Fire Dept.

“9/11 is really the turning point — it’s when everything changed and [terrorism] took a different path,” Gédéon Naudet says. The attacks in their native country in the past year are a prime example. “Unfortunately, it is the new normal,” Jules Naudet says. “Terrorism is here to stay.”

“9/11” previously aired three times on CBS — on March 10, 2002, and to commemorate the five- and 10-year anniversaries of the tragedy. The 2016 edition will feature a new intro from Denis Leary, who is closely aligned with advocacy for first responders. The updated material will focus on the ongoing health issues that 9/11 firefighters have battled, and the inspiring stories of
“legacy kids” — women and men who lost loved ones in the attack and have since become firefighters.

Hanlon retired from firefighting in 2007 to focus on his career as a TV director and actor. But seeing the “legacy kids” in action on the job reinforced the significance of the document that “9/11” provides.

In hindsight, Hanlon can’t believe they managed to collect so much material — particularly the in-the-moment experiences of individual firefights from Ladder 1 near the WTC — under such catastrophic circumstances.

“We pulled each guy who returned to the firehouse and made them record what happened that day,” Hanlon says. “Many years from now, when we’re all gone, people will look back and see what happened. And we didn’t put any spin on it. I’m proud of that historical record.”