Todd McEwen at Lit Hub:
North by Northwest isn’t about what happens to Cary Grant, it’s about what happens to his suit. The suit has the adventures, a gorgeous New York suit threading its way through America. The title sequence in which the stark lines of a Madison Avenue office building are “woven” together could be the construction of Cary in his suit right there—he gets knitted into his suit before his adventure can begin.
Indeed some of the popular “suitings” of that time, “windowpane” or “glen plaid,” reflected, even perfectly complemented office buildings. Cary’s suit reflects New York, identifies him as a thrusting exec, but also protects him, what else is a suit for? Reflects and Protects … a slogan Roger Thornhill himself might have come up with. The recent usage of calling a guy a “suit” if you don’t like him, consider him a flunky or a waste of space, applies to Cary at the beginning of the film: this suit comes barreling out of the elevator, yammering business trivialities at a mile a minute, with the energy of the entire building.