Stolen from French Nilm Noir Melville's 'Le Doulos'
The whole big gun thing tilted at the audience is from, as I see it, from the French auteur, Melville's Le Doulos from the 50's . Without giving away the plot of Le Doulos, the final scene has that famous 'Dirty Harry' big gun angle. It seems an obvious choice, but the original idea is Melvilles.
Also, where Harry shoots at the terrorist in the plane in the plane's washroom, that is a direct nod to Le Doulos where the lead shoots the ganster behind the screen. There is no doubt that the director Don Siegel has seen these Melville classic French movies. They set the standard, and themselves were influenced by the early American westerns and gangster movies.
Siegel is a very sharp guy and he brilliantly restaged this scene to a jet plane. Kudos to him for his brilliance and kudos to the French auteur Melville for creating the orignal idea for this. Who knows where he got the idea from.
Le Doulos was based on a novel, but I don't know whether the book set this up the way Melville did. See Le Doulos if you can and you will see where Siegel got some of his thinking from, which was a French reflection of original American movie making from a pre Dirty Harry time. Nothing is new under the sun.
My accountant says, 1 + 1, 40% of the time, equals divorce.