  The paper contributes towards the development of a unified control approach
for longitudinal aircraft dynamics with large flight envelopes. Prior to the
control design, we analyze the existence and the uniqueness of the equilibrium
orientation along a reference velocity. We show that shape symmetries and
aerodynamic stall phenomena imply the existence of the equilibrium orientation
irrespective of the reference velocity. The equilibrium orientation, however,
is not in general unique, and this may trigger an aircraft loss-of-control for
specific reference velocities. Conditions that ensure the local and the global
uniqueness of the equilibrium orientation are stated. We show that the
uniqueness of the equilibrium orientation is intimately related to the
so-called spherical equivalency, i.e. the existence of a thrust change of
variable rendering the direction of the transformed external force independent
of the vehicle's orientation, as in the case of spherical shapes. Once this
transformation is applied, control laws for reference velocities can be
designed. These laws extend the so-called vectored--thrust control paradigm
%developed for systems subject to orientation-independent external forces, e.g.
spherical shapes, to the case of generic body shapes subject to steady
aerodynamics.
