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.
On Mark Marksman C N60XX fitted with deepened pressurised fuselage, R-2800 engines and wing tip tanks
- Gunston, Bill (1993). World Encyclopedia of Aircraft Manufacturers. Annapolis: Naval Institute Press.