The Martin 4-0-4 was an American pressurized passenger airliner built by the Glenn L. Martin Company. In addition to airline use initially in the United States, it was used by the United States Coast Guard and United States Navy as the RM-1G.
Martin 4-0-4
United States Coast Guard RM-1Z/VC-3A.
The restored Martin 404 in 2008 at Camarillo Airport wearing Pacific Air Transport markings shortly before its last flight to Valle Airport
United States Coast Guard RM-1 in 1958.
An airliner is a type of airplane for transporting passengers and air cargo. Such aircraft are most often operated by airlines. The modern and most common variant of the airliner is a long, tube shaped, and jet powered aircraft. The largest of them are wide-body jets which are also called twin-aisle because they generally have two separate aisles running from the front to the back of the passenger cabin. These are usually used for long-haul flights between airline hubs and major cities. A smaller, more common class of airliners is the narrow-body or single-aisle. These are generally used for short to medium-distance flights with fewer passengers than their wide-body counterparts.
A United Airlines Boeing 737 (foreground) and a Virgin America Airbus A320 (background), two of the world's most widely used airliners
Sikorsky Ilya Muromets
The Douglas DC-3 appeared in 1935
Prototype of the de Havilland Comet in 1949, the first jet airliner in the world