These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
In his commentary, Ernest Lehman notes his regret that he can't take credit for the gag, as the script doesn't mention a tunnel.
Fridge Logic: If you're going to lure somebody to the middle of nowhere to kill him, why not do a drive-by instead of having a minion attack him from a crop duster? Hitchcock himself acknowledged the scene makes no sense, but justified it since nobody notices while watching the film.
Hitchcock himself developed a case of it for the scene where Eve and Leonard covertly talk using two phones at an airport. He held off filming the scene for a while, then apparently came up with a way it was possible and shot it, though he never told anyone what it was.