Capricorn One

1978's Capricorn One is a perfect example of that era's conspiracy films, in this case a faked manned landing on the planet Mars because budget cuts and shortcuts would have caused the death of the astronauts just weeks into their journey.

After initially agreeing to go along with the charade, the astronauts (James Brolin, Sam Waterston, and OJ Simpson) realize (too late, in my view) there's no way those involved with the conspiracy (likely the CIA, et. al.) can let them live due to the chance they might spill the beans. So, they manage to escape ... but the jet they commandeer has little fuel, and they have to ditch in the desert.

Brolin is the only one of the three who eludes those chasing him. In the meantime, reporter Elliot Gould manages to figure out the conspiracy, and eventually tracks down Brolin's location (with the assistance of "Kojak" star Telly Savalas). 

The end of the film shows Brolin and Gould arriving at a memorial service for the astronauts (the government's cover story was that their ship burned up during re-entry due to heat shield failure) to blow the lid off what arguably is the biggest conspiracy ever. But aside from the astronauts' way-too-late brainchild that they'll be killed regardless, the fact that Gould remained alive long enough to deduce the conspiracy is laughable.

This is because his best friend, who works for NASA and had begun asking questions regarding how some of the radio signals from the Mars launch just didn't add up (i.e. he was on the verge of figuring everything out), was expertly "disappeared" by the government -- so much so that even his landlord claimed he never remembered him.

But government intelligence was ridiculously inept when it came to Gould. First, they mess with his car so that its speed continues to increase while the brakes won't work; Gould somehow manages to evade everything, goes flying off of a drawbridge into a river, and manages to make it out alive. 

Second, someone tries to shoot him while he's investigating part of a cryptic message uttered by Brolin while was playing along with the government's ruse. Gould takes cover -- he just falls down on an open dirt road -- and there's no follow-up shot on the easy target!

Third, government intel operatives bust into Gould's apartment, plant cocaine, and then arrest him for it. But ... he gets bailed out by his editor! Like, why not just kill Gould then and there? Why not break into his apt. and poison, say, his iced tea? 

And to top off the "aw, c'mon"-style hilarity, Savalas and Gould rescue Brolin in a biplane and then manage to elude (and destroy) a pair of heavily armed choppers. Then Gould and Brolin somehow are permitted to drive right up to where the president of the United States is speaking (the astronaut memorial) without any Secret Service intervention. 

Alas, these were the days when Hollywood thrived on government conspiracy endeavors, most especially (or only) when committed by the Right, and portrayed the media as objective, looking-out-for-the-public Samaritans. (See here for how Capricorn One would be created under the Biden administration.)