I'm a programmer, and know a little about AI.
On the surface, it's much easier to build a self-flying machine than a robotic car or even a vacuum cleaner.
The space were you can fly is more or less well known, there are a number of accurate and independent positioning systems available,
the traffic is controlled so nothing should show up in front of the aircraft. The runways are equipped with ILS systems that guides the plane on
a perfect glide slope. The most problematic part might actually be to taxi from the runway and to park, as it's a visual process.
(Doesn't always work even today, I was once in a plane that got pushed into a light pole when leaving heathrow. It tooks some time to sort out, but at least
I can say that I have been in a airplane accident and walked away...)
However, it's a mistake to use these facts to conclude that's it's possible to build an autonomous airplane that's safe enough.
There are algorithms for obstacle avoidance, so it would be possible avoid most of the things that seems to be on a collision course,
and yes there are fuzzy or neural network based algorithms that seems to be able to adapt to damaged control surfaces and possibly
also missing or erroneous sensor data.
But to handle the sheer number of thing that can go wrong in complicated way, or even figure out that something has gone wrong,
requires more sophistication than we can currently create.
Things that are obvious to a human are surprisingly often extremely complicated to automate, like categorizing things,
detecting shapes, stand on one leg (or two) but stuff that we tend to think is hard normally isn't, like sudoku, long division, geometric calculations etc.
Even chess is just "semi-hard" though beating the best human players requires both clever algorithms and a significant amount of computation, .
We will build these machines, but I'm not flying with them until they are smarter than me.
I am certain that that day will come, eventually. Possibly in my own lifetime, and when that happens I think we will have much more interesting topics to discuss on slashdot than airplanes...