Longeron is a term used in aviation and refers to a structural component that runs the length of an aircraft's fuselage, typically made of metal or composite materials. Synonyms for this term include spar, beam, strut, rib, stringer, and frame. The spar is a particular synonym that refers to a structural member that runs diagonally and supports the wings of an aircraft. A beam is a synonym that refers to a long, horizontal structure that supports the weight of the fuselage. A strut is a support member that is used to brace or strengthen a structure. A rib is a narrow, curved structure that reinforces the shape of the fuselage. A stringer is a thin structural member that provides additional strength and stiffness. Finally, the frame is a complete structure that supports and shapes the entire aircraft.