Due to the increased demand for global connectivity, there has been a growing interest in the development and use of non-terrestrial networks (NTN) for applications (such as aeronautics) where terrestrial networks are not available or do not deliver satisfying performance. The use of newly deployed constellations in non-geostationary satellite orbits (NGSO) is getting much attention as it could potentially enable new performance levels in these applications, bridging the gaps of geostationary satellite orbit (GSO) systems. However, it has also lead to the need for more complex terminals, capable of continuously steering their beams towards the satellites. User terminals and their corresponding antennas become therefore crucial elements of the system. Its use in avionic systems has more features and constraints that are unique to the application. This paper focuses on the special constraints on the antenna terminal while taking into account an avionics satellite communication scenario and identifies potentialities and limitations of the use of NGSO systems as well as of the current technologies for airborne terminals.