Artist's impression of Martin 3-0-4 airliner.
This aircraft was first proposed to United Airlines in 1946.
Source: Evans, Stanley H. "American Notebook" Flight July 20, 1950 p. 93.
http://www.flightglobal.com/pdfarchive/view/1950/1950%20-%201369.html
An artist's impression of the 3-0-4 model which was to have been Martin's bid for the post-war turbopropped airliner, powered with General Electric TG-100s [XT 31]. Engine development fizzled out, however, and this Martin failed to hatch.
This aircraft was first proposed to United Airlines in 1946.
Source: Evans, Stanley H. "American Notebook" Flight July 20, 1950 p. 93.
http://www.flightglobal.com/pdfarchive/view/1950/1950%20-%201369.html