Stating the obvious
This is why Tesla never claimed the technology was fully autonomous, it was a more a driving aid that unfortunately worked too well.
If you fly a plane on autopilot and don't keep an eye on what its doing then you're quite likely to hit something or run into terrain. It won't happen very often because the sky is a big place but the technology won't cope with all unusual circumstance, it just reduces routine workload that allows the driver to focus on other tasks. Its the same with a car. Which is ultimately the problem with Tesla's technology -- it works too well so you can't stop people from believing it can do what it can't (and there are a lot more things to run into on the road than in the air)\.