Beware of explanations.
I haven't flown for a number of years now, and maybe things have changed, but when I flew transponders didn't have "squawk buttons." You just dialed in the code (four separate digit wheels) assigned by ATC. It's pretty hard to "accidentaly" dial in the hijack code unless one really intended to dial in the emergency code (7700, I think. And 7600 is used for something too.) instead.
ML/NJ
Right...don't transponders just have basically an off/standby/on switch, and then the buttons or dials for the code, and then the "ident" button that causes your information to flash or light up for the controller, so he can confirm it?
I can see somebody like me screwing up and accidentally putting 7500 in a transponder (momentarily), and I've heard stories about that happening before. But somebody flying an A330 or A340 across the Atlantic with 271 people onboard? Both members of the crew are NOT going to be newbies. That's a huge screwup, if that's what it is.
}:-)4
There is a squawk button, but all pilots I know and all air traffic controllers I know refer to it as the "ident" button since pressing the button lights up your blip on the controllers' radar screen. I had to use it once when I was doing my first long cross-country flight from Manchester, NH to Bangor, ME and got lost in northern Maine (once you leave the Portland area there's nothing to navigate by but lakes if you screw up your navigation planning, and there are a ton of them in northern Maine). The Bangor tower asked me to "ident". I did and they were able to vector me in to airport from where I was.