The Martin 146, designated by the manufacturer as Model 146, was a single experimental prototype bomber developed in 1935. The aircraft was designed to compete in the United States Army Air Corps' "Project A" competition, a high-stakes effort to develop a new generation of heavy bombers. In this competition, the Martin 146 faced off against other notable designs, including the Douglas DB-1 and the Boeing Model 299, the latter of which would eventually evolve into the B-17 Flying Fortress.
Constructed by the Glenn L. Martin Company, the prototype was built at the company's primary aircraft works in Middle River, near Baltimore, Maryland. The firm had relocated to this area in 1929 and had established itself as a premier producer of military aircraft. The Model 146 continued the company's commitment to all-metal, low-wing monoplane construction, a design philosophy that had previously proven revolutionary with the B-10 series. Due to its confidential nature during development, the aircraft was frequently referred to in period accounts as a "mystery bomber."
While the exact date of its first flight is not documented, the aircraft was operational by late summer. On August 21, 1935, Captain William E. Ebel of the Air Corps delivered the Martin 146 to Wright Field for official evaluation. The aircraft was a twin-piston-engined monoplane, though specific details regarding the engine manufacturer, model, and horsepower remain unknown. Following its evaluation at Wright Field between 1935 and 1936, the U.S. Army did not order the aircraft into production. Consequently, only one airframe was ever constructed.
Because the Martin 146 never entered series production, it saw no operational service and did not participate in any military conflicts. Its legacy is primarily that of a technological stepping stone in the evolution of American heavy bombers. The sole prototype is no longer in existence and is believed to have been scrapped, as it is not listed in the holdings of the Glenn L. Martin Maryland Aviation Museum or other major collections. The Glenn L. Martin Company itself eventually merged with the American-Marietta Corporation in 1961 to form Martin Marietta, which later merged with the Lockheed Corporation in 1995 to become the modern aerospace giant Lockheed Martin.