It seems there has been a misunderstanding in terminology. It is correct that the definition of Angle of Attack can be the angle between the aerofoil and the relative airflow. As a fighter pilot, I can relate to your practical example. However, in accordance with the Airplane Upset Recovery Training Aid (URTA), the internationally recognized standard, the broader scope definition of Angle of Attack is the angle between a reference line and the relative airflow as follows: URTA 2.5.5.1 -

“Depending on the context in which it is used, aerodynamicists use the term ‘angle of attack’ in a number of ways. Angle of attack is always the angle between the oncoming air, or relative wind, and some reference line on the airplane or wing. Sometimes it is referenced to the chord line at a particular location on the wing; sometimes to an ‘average’ chord line on the wing; other times it is referenced to a convenient reference line on the airplane, like the body reference x axis. Regardless of the reference, the concept is the same as are the consequences: exceed the critical angle of attack and the lifting surfaces and wind will separate, resulting in a loss of lift on those surfaces. Frequently the term ‘airplane angle of attack’ is used to refer to the angle between the relative wind and the longitudinal axis of the airplane. In flight dynamics, this is frequently reduced to simply ‘angle of attack’.”

… as the Flight Path Angle represents the orientation of the relative airflow in reference to the horizon and pitch attitude is also in reference to the horizon (often representative of the bore line or longitudinal axis of the fuselage), it is equally correct to state Angle of Attack can be the angle between the flight path angle and the pitch attitude. In your fighter aircraft example, the flight path of the airplane is 90 degrees nose up as is the the pitch attitude. Hence, the AOA is near zero or possibly even slightly negative if the aerofoil is asymmetric and the flight path is sustaining a vertical up line over time. Of more use to pilots unable to clearly picture AOA, to coin a phrase from one of our respected colleagues Mr. John Cox, CEO of Safety Operating Systems: “Angle of Attack is simply the difference between where the wing is pointing and where the wing is going …”

This is an important topic Mathias, and I’m glad you initiated the discussion.