A structural assembly of an aircraft, the assembly comprising: a fuselage portion comprising an aft pressure wall; and a wing unit configured to be assembled with the fuselage portion, the wing unit comprising a first wing extending in a first lateral direction relative to the fuselage portion and a second wing extending in an opposite second lateral direction relative to the fuselage portion, the first wing and the second wing being attached together; wherein: the fuselage portion and the wing unit are attached together at a first structural interface between the fuselage portion and the wing unit; the fuselage portion and the wing unit are unattached at a second structural interface between the fuselage portion and the wing unit, the second structural interface not having final in-use positional constraints between the wing unit and the fuselage portion; the first structural interface being configured to permit relative positional adjustment between the wing unit and the fuselage portion while the fuselage portion and the wing unit are attached at the first structural interface and unattached at the second structural interface to permit incorporation of final in-use positional constraints between the wing unit and the fuselage portion in the second interface while the fuselage portion and the wing unit are attached at the first interface and after the relative positional adjustment; and characterized in that the first structural interface comprises at least one aft tension fitting for attachment with the aft pressure wall of the fuselage portion, the at least one aft tension fitting comprising an oversize hole formed therein for receiving a bolt, the oversize hole being oversized relative to the bolt to provide an allowance permitting said relative positional adjustment between the wing unit and the fuselage portion; and wherein the at least one aft tension fitting is disposed outside of the wing unit. a fuselage portion comprising an aft pressure wall; and a wing unit configured to be assembled with the fuselage portion, the wing unit comprising a first wing extending in a first lateral direction relative to the fuselage portion and a second wing extending in an opposite second lateral direction relative to the fuselage portion, the first wing and the second wing being attached together; wherein: the fuselage portion and the wing unit are attached together at a first structural interface between the fuselage portion and the wing unit; the fuselage portion and the wing unit are unattached at a second structural interface between the fuselage portion and the wing unit, the second structural interface not having final in-use positional constraints between the wing unit and the fuselage portion; the first structural interface being configured to permit relative positional adjustment between the wing unit and the fuselage portion while the fuselage portion and the wing unit are attached at the first structural interface and unattached at the second structural interface to permit incorporation of final in-use positional constraints between the wing unit and the fuselage portion in the second interface while the fuselage portion and the wing unit are attached at the first interface and after the relative positional adjustment; and characterized in that the first structural interface comprises at least one aft tension fitting for attachment with the aft pressure wall of the fuselage portion, the at least one aft tension fitting comprising an oversize hole formed therein for receiving a bolt, the oversize hole being oversized relative to the bolt to provide an allowance permitting said relative positional adjustment between the wing unit and the fuselage portion; and wherein the at least one aft tension fitting is disposed outside of the wing unit.