On Mark Engineering was an American aircraft remanufacturing company established in 1954 at Van Nuys Airport in California. Its most significant products were rebuilding military surplus A-26 Invaders into executive transports—the Marketeer with an unpressurized fuselage and the Marksman with fuselage pressurization. On Mark converted 41 Douglas B-26s into one YB-26K and 40 B-26K Counter-Invaders (later redesignated A-26A) for counterinsurgency missions with the US Air Force. On Mark also undertook conversion work of a Boeing 377 Stratocruiser into the prototype Pregnant Guppy for Aero Spacelines. Products On Mark Executive On Mark Marketeer On Mark Marksman B-26K Counter-Invader Aero Spacelines Pregnant Guppy—prototype only References External links Marksman by Airscene org uk A site on Van Nuys Airport, including On Mark Engineering Defunct aircraft manufacturers of the United States Technology companies based in Greater Los Angeles Manufacturing companies based in Los Angeles Manufacturing companies established in 1954 Technology companies established in 1954 1954 establishments in California Defunct manufacturing companies based in Greater Los Angeles