Click Hamilton wrote:
I never thought about that much. A pilot should be looking in all directions, including above and below. To see past the cowl on a tail-dragger the pilot should taxi with drunken-looking S-turns so he can look ahead from looking side to side. Without that, he could run into something. A tail-dragger with a big engine is worse. Can't see anything straight ahead.

Before entering the runway, for example, it's a good idea to lock one wheel brake and do a 360 on the ground for an excellent view of the airspace around the airport in all directions. If it's clear, then announce on the radio, pull out and full throttle.

In level flight the plane visibility is relative to level flight. You can see the ground from the left or right, but not down through the front of the airplane. In a nose-down descent the visibility of the ground is better if you want to look at it straight ahead. In a climb, the pilot can only see what he can see at that angle pointing upwards in the direction he's flying, not "straight ahead" .. meaning relative to the ground.  The views and blind spots change with the planes attitude to the relative wind.

In a plane with tricycle landing gear, the body of the plane is already in a more level configuration when on the ground.

Yes, there are significant blind spots, but it depends on what the pilot should be looking at. Wings are big blind spots too. The pilot can raise and dip wings to check out airspace around him or to get a better view of the ground, if that's important. It seems natural to do this for a look before making sharp left or right turns. The movement is subtle and maybe the passenger doesn't notice.

Before a pilot does a maneuver that's an abrupt departure from straight and level (stall, dive, acrobatics, other sharp changes) the pilot should do a 90 degree turn one direction, then 180 back the other, or make a 360 steep turn to make sure the area is clear. By doing this the pilot can see clearly in all directions and make sure there are no other aircraft in his area.

In a car, it's about looking left or right, straight ahead and for cops in the rear view mirror. In a plane you also have to look above and below.

Coming in for a landing, for example, power is reduced or cut and the nose comes up to bleed off the energy and slow the plane down for a gentle descent (sink, not dive) to the runway. There is a huge blind spot trying to look through the engine if it's in front of you, or over the nose. There are lots of other reference points all around, including the left and right edges of the runway. Perspectives. Trapezoidal shapes. Looking down is different from looking across. This is part of what telIs a pilot where he is. That perspective is different from the pilots seat of different aircraft. Maybe that feeling is part of the thrill of flying. 

I've never seen my wheels touch the ground either. That view is not available to me through the floorboards. You just learn to know when the wheels are going to touch. You feel for it.

There's an old expression: "flying by the seat of your pants" ... you can feel a lot of things through your butt, LOL, like where the ground is. 

Planes in a pattern can descend upon one another on the final approach if they don't see each other. Different planes have different landing speeds and rates of descent. There are blind spots from both positions. Especially at an airport without a control tower, It's good practice to announce your position in the pattern and when entering the different segments of the landing pattern (left pattern, right pattern, entering downwind from the 45, downwind, turning left or right base, straight in, turning final, etc.) This gives other pilots more of a chance to see each other.
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To answer your question, I think looking around the head of a passenger sitting in the front seat is a very minor consideration relative to all the other things a pilot should be looking at, or being aware of indirectly. The passengers head might block the view of part of the instrument panel, but that's about all. A pilot can see a lot from unobstructed side views.

thanks for the very informative response, click. that all makes sense, and answers a lot of questions i had; me being a non-pilot,