That video is awesome!!
He mustve flipped over vertically
Actually, it looks like all he did was pull a negative-G by climbing the airplane and then letting the nose fall rapidly so that they pulled a negative-G dive. I think if he did a full loop, centrifugal force would have actually pushed the dog and the other objects/humans down in there seat.
Awesome video, though! I've always gotten a kick out of this one.