Not very comfortable when I get beyond the height of the roof of my house......I guess that is about as far as I would care to fall. Been flying 36 years and never an issue in the airplane. Doesn't even enter the brain it seems. Thought for a long time that it was perhaps a question of "being in control" but suddenly dawned on me one day that it isn't an issue when riding in the back either. Moved on to a theory of being in an "enclosed" vessel but that doesn't work out either as I can go up in an open cockpit and the willies don't raise their head but can have that feeling standing against the window of a tall building.....so not sure what is at play.