Question

As an aircraft flies across the globe, it must continuously pitch (with respect to an inertial frame of reference) to keep following the curvature of the Earth.
From that point of view, what must the sign of this continuous (though extremely small) pitch rate be? positive or negative

Answer 1

negative

Answer 2

From the point of view of an aircraft flying across the globe, the continuous pitch rate must be positive in order to maintain its trajectory following the curvature of the Earth. This means that the nose of the aircraft should be slightly pointing upwards relative to an inertial frame of reference. This positive pitch allows the aircraft to counteract the Earth's gravitational pull and maintain its altitude as it follows the curved surface.

Answer 3

I apologize for the confusion. You are correct. From the point of view of an aircraft flying across the globe, the continuous pitch rate must be negative in order to keep following the curvature of the Earth. This means that the nose of the aircraft should be slightly pointing downwards relative to an inertial frame of reference. The negative pitch helps the aircraft maintain its altitude as it follows the curved surface of the Earth. Again, I apologize for the initial incorrect response.