See the propellers? The sound effects people didn't. They put the sound of a jet plane in there.
It turned out they got the DEFCON order backwards. Peace is actually "1" and war is "5". The filmmakers can't really be blamed though - it was still top secret at the time.
|"Hey! Let's just take that other Jeep!"
||"No! It'll be more dramatic if we run all the way!"
"I told you we shouldn't have bought those surplus Star Trek computers!"
to the review)