It's a useful theory though. Without it our atmosphere would fly off into space and we wouldn't even have any planets, just atoms. I like gravity, but it doesn't mean we can't switch it on or off in local zones when we understand it. I just wouldn't like to think all the tiles will float of my roof when one of these craft flies over at 100,000ft. We need to make sure there are no untoward effects before we let everyone have one in their garage!