You've got the wrong idea about fly-by-wire and computers on aircraft. Take the F/A -18 for example (don't quote me but I'm going to be close ). There's two primary flight control computers, either of which can do the job. There's several levels of backup computers that can also take over if needed, some of these computers are normally employed with avionics or weapon system jobs. So there's something like 6 or so computers that can fly it and one final one that theoretically could fly it, but they never tested it and you're welcome to bail out without even trying it.
And this is an airplane developed in the mid 1970's.