From looking at the box art on this Marx No. J-9569 Military Jet Plane it very much appears to be a Lockheed C-141 Starlifter. The C-141 first flew in 1963 and was meant as a replacement for the slower prop-driven cargo haulers of the time. It flew for the Military Air Transport Service), its successor the Military Airlift Command (MAC), and finally for the still current Air Mobility Command (AMC) and was finally retired in 2006 after being replaced by the C-17 Globemaster III.
Marx seems to have been very cautious in not using the actual name of the aircraft perhaps due to licensing concerns. The toy is 'selectively compressed' to mimic the basic look of the prototype but it has a much shorter fuselage than the real thing. Like many of my toys this one displays well. It came with a box in great condition and the original instructions on wafer thin paper but the four plastic wing attachment lugs are broken off causing the wing assembly to just sit on top of the fuselage without a nice snug fit. I really like how the Marx logo on the fuselage also has the year of manufacture - '1965'. Too often it's hard to pin down exactly when these gems were made. The toy measures 14" (35.56cm) L x 14 1/2" (36.83cm) wingspan x 4 5/8" (11.74) H and normally would have lights, sound, and action. Enjoy! Opa Fritz and Oma Bettina