Any zero G situation while in the vicinity of a planet, including while in orbit, is due to the effect of free falling. Pushing the nose over is the same physical effect as 'falling around the planet', which is what happens in orbit - your forward momentum is offset by the pull of gravity, curving your trajectory towards the earth instead of leaving orbit at a tangent. As you fall, you continue to travel forward and you end up continuously falling around the planet. That is how the moon orbits the earth (and the planets orbit the sun). (As a side note, the moon has enough mass to generate its own measurable gravity, irrespective of the planet around which it orbits.)
You have to get quite a large distance from any celestial objects to experience a complete "lack of gravity", and I venture to say that humans have not yet traveled that far from earth (depending upon what threshold you use I suppose). A space vehicle the same distance from the earth as the moon, without any relative velocity, will eventually fall back to earth.