Ten minutes rarely make a feature as unforgettable as Clint Eastwood’s latest directorial effort, an ode to American servicemen who put their lives on the line for strangers they’ll never truly know.

No feat of filmmaking can ever truly express the amount of heroism shown by Spencer Stone, Alek Skarlatos and Anthony Sadler as well as three other European men on a seemingly random train ride across Europe.

Try as he might, Eastwood’s latest biopic drama “The 15:17 to Paris” would be better served as a 20-minute short film rather than a 90-minute feature as the climatic third act overwhelmingly dwarfs the film’s haphazard, lazy first hour.

Three friends, along with several unnamed European travelers, thwart a terrorist attack on a train from Amsterdam to Paris. Based on true events, “The 15:17 to Paris” builds from a slow beginning to a gripping climax as Spencer, Alec and Anthony leap into action while on a leisurely trip across Europe.

In a bold twist, Eastwood cast the actual heroes to play themselves for much of the film. This gives “15:17 to Paris” unmatchable authenticity that feels increasingly voyeuristic over the course of 90 minutes. Yet at the same time, there’s something seemingly unsettling about washing American heroes reliving imminent danger and potentially traumatic acts of terrorism.

Casting the real men to play themselves gives “15:17 to Paris” a leg up in realism as Stone, Skarlatos and Sadler overcome their acting inexperience with a committed, inspirational effort.

In attempting unparalleled authenticity, Eastwood veers widely off course at times, most likely due to a poorly-written screenplay from first-time writer Dorothy Blyskal. Her haphazard adaptation fails to do even remote justice to the heroism of three Americans, not to mention the English and French businessmen on the train who risked their lives to save countless others.

There’s a lot of weird, random things in “15:17 to Paris,” but none more so than the outlandish, almost unbelievable scene where Spencer and Anthony take a bike tour in Germany led by a guide who sings “Springtime for Hitler” from Mel Brooks’ “The Producers” in one of the decade’s wildest left turns.

“15:17 to Paris” also becomes burdened with social commentary, lamenting attention deficit disorder diagnosis with throwaway lines like “My God is bigger than your statistics” and Anthony’s dated obsession with a selfie stick.

Told in traditional biopic fashion, Blyskal’s bland screenplay languishes in an over-exerted preamble to the actual attack, referencing moments briefly to keep audiences’ attention before diverting back to an hour’s worth of vapid, amateurish dialogue.

When the attack actually occurs, Blyskal and Eastwood rush through the aftermath in an attempt to wrap things up in a neat little bow. Viewers never get a clear picture of the impact terrorism has on the subjects it victimizes or the psychological ramifications these American heroes are placed under.

It’s easy to forget how languishing, emotionally detached the prior 75 minutes are when the film’s final 15 are so outstanding. Viewers can rightfully pay full price for the third act of “The 15:17 to Paris.”

Patience and the proper mindset will be paramount for audiences until the train leaves the station.

In his later years, Eastwood has defined his directorial career with vivid, cinematic biopics honoring the legacy of true American heroes. A weak screenplay devastate any real chance Eastwood had of telling this tale on the same cinematic or emotional level as Chester Sullenberger’s in 2016’s “Sully” or Chris Kyle’s in 2014’s outstanding “American Sniper.”

Without a doubt, stories like these need to be told on the big screen as a reminder of what it means to be American. Unfortunately, Hollywood hasn’t quite hit the mark with a film unlikely to age well.

In spite of its many flaws, “The 15:17 to Paris” is a film that deserves a wide audience that can truly appreciate and become inspired by the heroism of ordinary people doing extraordinary things.