I don't really know the entire genesis of it. I know that the program manager around the time of the 737NG acquisition was (is) a former F-15 pilot who was very enamored with the HUD capability offered on the NG. And, to be fair, rightly so...it is a very powerful tool. I suspect that a certain amount of the impetus toward HUD was that a) it was capable of CAT III fail-passive, and b) in order to use the HUD for CAT I or CAT II, and then autoland for CAT III, you'd have to add a bunch of training time to all blocks of training. I believe there was an effort to add autolanding to the program several years ago, but that was rejected for the above reasons.
That said, I have done both...fail-operational autoland in the 767/757, fail-passive autoland in the MD80 (
), and fail-passive HUD landings in the 737NG. They are all good options, INMHO. And we can fly single engine CAT III approaches on the HUD, which I don't think would be an option with autoland on the NG. Of course, feel free to calculate the statistical probability of needing that capability here in the States. We get some relief on alternates from it, but big deal.