I make flying stuff all the time. Not as heavy but I don't see a reason why I couldn't and I won't need a couple of billion to do so. This thing 'flies' for a very narrow definition of flying. Call me when it stays in the air for a couple of minutes. Prediction: that will never happen.

We've had variations of flying cars for 60+ years. We know how to build them.

What people mean by "flying cars" is mass production. Ford Model T.