You Can't Win 'Em All
When the biplanes strafe the trucks they let out the iconic 'jericho trumpet' sound of a WWII Stuka dive bomber. Also, they should hardly be over-revving anyway in a strafing and bombing role.
The movie is set in 1922, but a contemporary Canadian flag appears on the wall in the tavern. In 1970, when the film was made, the Canadian flag shown had only existed for five years.
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