Integration and convergence of different access technology is a key concept of 4G systems. This integration also includes the interface among terrestrial and aero-space components, whose importance has been so far under-estimated and not deeply understood. In this paper, a layered model of the 4G integrated network vision is introduced, highlighting details about the aero-space component. The concept of integration is discussed under different viewpoints, particularly highlighing integration among aero-space segments and related services (i.e. navigation). Examples of integration scenarios identified and investigated in the frame of research programs co-funded by Italian institutions are also displayed in the paper.