During the past decades quite a variety of endocytic pathways have been identified in eukaryotic cells [8, 9, 10] . Their occurrence, abundance and mechanistic details appear to vary between cell types, tissues and species and their utilization by viruses as a route of entry makes them an important factor in host and cell-type permissiveness for infection [11, 12] . Besides by CME, different viruses have been shown to enter cells via caveolae, macropinocytosis or other, less well described, routes [11, 12] . Most often, the selection of a specific endocytic route is linked to the utilization of a specific receptor that facilitates traveling via that particular route. Nevertheless, many receptors allow flexibility by their capacity to enter through multiple pathways. For IAV, an additional level of complexity to the dissection of potential entry routes is added by the apparent lack of an IAV-specific protein receptor.