IIRC it's all the airspace until the 'general aviation' zone starts, where the owner still has some control but FAA or other local authority legally requires property owners to permit operation of planes and other properly licenced aircraft.

There's not much court precedent yet, and many places are passing specific laws to clarify this, but the general assumption should be that unless you're above 400-500 feet where national aviation regulations apply, you'd need a permission from the owner of the land.

Could I destroy an RC vehicle driven onto my land property? The laws should be the same for both, although I'm not banking on it.

The general principle seems to be that things owned by others remain so even if they are on your property, and intentionally damaging them is vandalism. E.g. if you notice someone's car parked on your land and smash its windows, that'd be a crime even if that car "has no right to be there" - you could require the car to leave in some legal manner, possibly have it towed or sue for damages caused by it being there; but breaking other people's stuff is one of the oldest things prohibited by law.

Could you? Sure! Could you legally destroy it? As they say, "possession is nine-tenths of the law."

I read "over your property" as already implying that the airspace isn't your property.

I honestly didn't/don't know. How far do you own down?

Depend of the country, in France it's to the center of the earth, which means you receive some money when they build a metro under your house becaude they buy a right to use part of your property.

In UK I'm pretty sure it's nothing, certainly you don't get anything (money/rights) if oil or coal is extracted from beneath your property ... but then people are allowed - with planning permission - to build down from established property. I expect the Crown owns it all.