A method of securing a split winglet to a wing tip of an aircraft includes fastening an upper winglet to an upper winglet attachment portion of a wing attach fitting having a wing attachment portion. The method further includes fastening a lower winglet to a lower winglet attachment portion of the wing attach fitting. The method additionally includes fastening the wing attachment portion to the wing tip using tension fasteners installed from an inboard side of the wing tip to secure the split winglet to the wing.