Owning a ghost gun is a crime, right?

(Ignoring the fact that “ghost gun” is a meaningless and intentionally emotionally charged term)

In New York, yes. In the vast majority of the US, no. It’s illegal to file the serial number off an existing firearm, but 100% legal in most states to manufacture your own unserialized firearms for personal use. Just cannot be sold/transferred.

I’d note the article you linked says nothing about how many of those are actually 3D printed, it is infinitely easier to deface the serial number on an existing firearm than it is to 3D print one.

Not saying it’s a good idea, but a lot of the complexity surrounding automated driving is actually because you are confined to a 2D space and have to follow roads/road signs. When you can just lift off and adjust verticality to avoid objects all you really need is a way to detect and avoid obstacles and some navigation logic. Landing is probably the most difficult part to automate.

Not super easy but it is actually easier than self-driving cars (which is why almost all of a commercial flight is running on autopilot)