In the early part of the movie Brendon was kicked out of Matt's Saloon in Prescott. He then walked down the street and a horn of a train was heard in background. The last train to go through Prescott was in 1962.
Further to the helicopter registration comment that US registrations are 5 or fewer characters after the N, the 0 after the N in N0312DF is invalid. The first character after the N (or after NC, NX, etc. for old registrations) must be a digit 1 - 9.
The red and white Bell 204/205 helicopter shown taking the crew up to their first Hot Shot evaluation, ship 202, has a registration number of N0312DF. This is a civilian helicopter, with a civilian N-Number, but US civilian N-Numbers are only five characters, this one has six. This is obviously a made up registration number, as it can't (and doesn't) exist in real life. The second Bell 204/205 seen during this extraction, ship 203, also has a fake six character N-Number, N1979DF.
When Amanda leaves Duane's house in her truck, one of the crew member's feet can be seen reflected in the truck's chromed front bumper.
although the movie is set in Arizona based on the tragedy/true story of the Granite Mountain Hotshots it was filmed entirely across the border in the state of New Mexico.