At the age of 87, Clint Eastwood doesn’t waste time.

The prolific director’s “The 15:17 to Paris” comes just two and a half years after the real-life incident upon which it is based, when a handful of passengers on a Thalys train from Amsterdam to Paris subdued a heavily armed gunman.

Famous for shooting his films quickly and efficiently and not dallying over multiple takes, Eastwood made the film last summer and turned in a final product with a running time of just 94 minutes.

Eastwood even took a shortcut, so to speak, when it came to casting. When he met with the three American heroes from the train — Spencer Stone, Anthony Sadler and Alek Skarlatos — he abandoned the idea of hiring professional actors and cast the men to play themselves. (It’s not unprecedented in Hollywood history to cast non-actors in lead roles or even to have certain figures play themselves, but it’s a rare and extraordinary step.)

REVIEW

A number of passengers on the train — including a Virginia man who was shot and critically wounded but survived — also play themselves in “The 15:17 to Paris,” adding to the docudrama feel of the movie. No doubt it was cathartic for many to return to the moment and relive it, knowing they were going to come out alive.

Unfortunately, even though of course we recognize the bravery and selfless heroism of the men on that train who risked their lives to save others, and even though there are a few pulse-quickening moments in “The 15:17 to Paris,” the movie is slow-paced and feels padded, even with that running time of just over an hour and a half.

And while the three real-life heroes gamely try to re-create their own histories, from the years and months and moments leading up to the attack to their bold and decisive actions on that train, they are amateurs, and they come across as such. Although much of the dialogue was reportedly improvised and the guys clearly are good friends, the dialogue often comes across as flat and somewhat stiff.

Working from a screenplay by Dorothy Blyskal (who adapted a book by Jeffrey E. Stern and the three Americans), Eastwood spends a lot of time — too much time — on the backstories of Spencer, Anthony and Alek, who bonded over some light troublemaking escapades in middle school in the mid-2000s and delighted in playing war games in the woods.

We get numerous scenes of Spencer’s single mother, Joyce (Judy Greer), and Alek’s single mother, Heidi (Jenna Fischer), meeting with school principals or fretting over their mischievous sons. (We don’t see anything of Alek’s home life.)

There’s nothing particularly poignant or dramatic, no pivotal moment, in the boys’ upbringing. It seems to take forever before we’re catapulted a decade forward and we meet up with Spencer, now with the United States Air Force; Alek, a member of the Oregon National Guard, and Anthony, a student at California State University in their hometown of Sacramento.

The three of them meet up in Europe for an extended vacation. While Alek hangs out with a girl in Germany, Spencer and Anthony see the sights in Rome, with Anthony’s ever-present Selfie Stick helping them capture their times at the Colosseum, the Vatican, the Trevi Fountain, etc. Eventually the guys meet up and go dancing in Amsterdam, and then debate whether or not to visit Paris.

Occasionally and for the briefest of moments, Eastwood flashes forward to the incident on the train. But then it’s back to the travelogue, and Spencer talking in philosophical terms about how maybe there’s a larger purpose in store for them.

(The structure of “The 15:17 to Paris” is not dissimilar to the framing of Eastwood’s “Sully,” which took us deep into the movie before we actually saw the water landing on the Hudson.)

Once we’re on the train and events play out, “The 15:17 to Paris” shifts gears and becomes a taut thriller, effectively conveying the chaos and terror that erupted on the train — and the great heroics of the American, British and French passengers who took down the gunman.

It’s impossible to say whether “The 15:17 to Paris” would have been a better movie with professional actors in the lead roles. All we can do is go with what we’ve got, and while acknowledging and saluting and admiring these men and what they did on that train, the story as told here feels more suited for a hourlong documentary than a feature film.

★★

Warner Bros. presents a film directed by Clint Eastwood and written by Dorothy Blyskal, based on the book by Anthony Sadler, Alek Skarlatos, Spencer Stone and Jeffrey E. Stern. Rated PG-13 (for bloody images, violence, some suggestive material, drug references and language). Running time: 94 minutes. Opens Friday at local theaters.