  Space-Air-Ground Integrated Networks (SAGINs), which incorporate space and
aerial networks with terrestrial wireless systems, are vital enablers of the
emerging sixth-generation (6G) wireless networks. Besides bringing significant
benefits to various applications and services, SAGINs are envisioned to extend
high-speed broadband coverage to remote areas, such as small towns or mining
sites, or areas where terrestrial infrastructure cannot reach, such as
airplanes or maritime use cases. However, due to the limited power and storage
resources, as well as other constraints introduced by the design of terrestrial
networks, SAGINs must be intelligently configured and controlled to satisfy the
envisioned requirements. Meanwhile, Artificial Intelligence (AI) is another
critical enabler of 6G. Due to massive amounts of available data, AI has been
leveraged to address pressing challenges of current and future wireless
networks. By adding AI and facilitating the decision-making and prediction
procedures, SAGINs can effectively adapt to their surrounding environment, thus
enhancing the performance of various metrics. In this work, we aim to
investigate the interplay of AI and SAGINs by providing a holistic overview of
state-of-the-art research in AI-enabled SAGINs. Specifically, we present a
comprehensive overview of some potential applications of AI in SAGINs. We also
cover open issues in employing AI and detail the contributions of SAGINs in the
development of AI. Finally, we highlight some limitations of the existing
research works and outline potential future research directions.
