Assemblies and methods for facilitating the assembly of aircraft wings to a fuselage are disclosed. In some embodiments, a wing unit includes features that are configured to define one of more parts of a pressure vessel that is partially defined by the fuselage portion. In some embodiments, the aircraft assemblies disclosed herein comprise one or more first structural interfaces that permit positional adjustment between the wing unit and the fuselage portion so that one or more second structural interfaces may be finished only after such positional adjustment. In some embodiments, the aircraft assemblies disclosed herein comprise one or more structural interfaces that are disposed outside of the wing unit in order to eliminate or reduce the need for assembly personnel to access the interior of the wing unit to carry out the structural assembly of the wing unit to the fuselage portion.