The Northrop YB-35/XB-35, Northrop designation N-9 or NS-9, were experimental heavy bomber aircraft developed by the Northrop Corporation for the United States Army Air Forces during and shortly after World War II. The airplane used the radical and potentially very efficient flying wing design, in which the tail section and fuselage are eliminated and all payload is carried in a thick wing. Only prototypes and pre-production aircraft were built, although interest remained strong enough to warrant further development of the design as a jet bomber, under the designation YB-49.
The Boeing XB-15 was a United States bomber aircraft designed in 1934 as a test for the United States Army Air Corps (USAAC) to see if it would be possible to build a heavy bomber with a 5,000 mi (8,000 km) range. For a year beginning in mid-1935 it was designated the XBLR-1. When it first flew in 1937, it was the most massive and voluminous airplane ever built in the US. It set a number of load-to-altitude records for land-based aircraft, including carrying a 31,205 lb (14,154 kg) payload to 8,200 ft (2,500 m) on 30 July 1939.
The Huff-Daland XB-1 was a prototype bomber aircraft built for the United States Army Air Corps.
The Curtiss B-2 Condor was a 1920s United States bomber aircraft. It was a descendant of the Martin NBS-1, which was built by the Curtiss Aeroplane and Motor Company for the Glenn L. Martin Company. There were a few differences, such as stronger materials and different engines, but they were relatively minor.
The Martin XB-16, company designation Model 145, was a projected heavy bomber designed in the United States during the 1930s.
The Douglas XB-19 was a four-engined, piston-driven heavy bomber produced by the Douglas Aircraft Company for the United States Army Air Forces (USAAF) during the early 1940s. The design was originally given the designation XBLR-2. It was the largest bomber built for the USAAF until 1946, with the Convair B-36 surpassing it in size.
The North American XB-21 and sometimes referred to by the name "Dragon", was a prototype bomber aircraft developed by North American Aviation in the late 1930s, for evaluation by the United States Army Air Corps. Evaluated against the Douglas B-18 Bolo, it was found to be considerably more expensive than the rival aircraft, and despite the ordering of a small number of evaluation aircraft, only the prototype was ever built.
The Douglas XB-31 was the design submitted by Douglas after the request by the United States Army Air Forces for a very heavy bomber aircraft, the same request that led to the Boeing B-29 Superfortress, Lockheed XB-30, and Consolidated B-32 Dominator.
The Nakajima G8N Renzan was a four-engined long-range bomber designed for use by the Imperial Japanese Navy. The Navy designation was "Type 18 land-based attack aircraft" (十八試陸上攻撃機); the Allied code name was "Rita".
The Boeing XB-39 Superfortress was a United States prototype bomber aircraft, a single example of the B-29 Superfortress converted to fly with alternative powerplants. It was intended to demonstrate that the B-29 could still be put into service even if the first choice of engine, the air-cooled Wright R-3350 radial engine, ran into development or production difficulties.
The XB-38 Flying Fortress was a single example conversion of a production B-17E Flying Fortress, testing whether the Allison V-1710 V type engine could be substituted for the standard Wright R-1820 radial engine during early World War II.
The Convair XB-53 was a proposed jet-powered medium bomber aircraft, designed by Convair for the United States Army Air Forces. With a radical tailless, forward-swept wing design, the aircraft appeared futuristic; however, the project was canceled before either of the two prototypes were completed.
The Martin XB-48 was an American medium jet bomber developed in the mid-1940s. It competed with the Boeing B-47 Stratojet, which proved to be a superior design, and was largely considered as a backup plan in case the B-47 ran into development problems. It never saw production or active duty, and only two prototypes, serial numbers 45-59585 and 45-59586, were built.
The Boeing YB-9 was the first all-metal monoplane bomber aircraft designed for the United States Army Air Corps. The YB-9 was a much enlarged twin-engine development of Boeing's single-engine Model 200 Monomail commercial transport.
The Boeing B-54 was an American strategic bomber designed by Boeing for use by the United States Air Force. Derived from the YB-50C Superfortress, construction of the prototype was canceled before completion, and the aircraft was never flown.
The Boeing XB-55 was a proposed Boeing aircraft designed to be a strategic bomber. The XB-55 was intended to be a replacement for the Boeing B-47 Stratojet in United States Air Force (USAF) service.
The Boeing XB-56 was a proposal by Boeing for a re-engined version of the American jet-powered medium bomber aircraft, the B-47 Stratojet. The original designation for this modification was YB-47C.
The Allison V-3420 was a large experimental piston aircraft engine, designed in 1937 by the American Allison Engine Company.
The Douglas XB-43 Jetmaster is an American 1940s jet-powered prototype bomber. The XB-43 was a development of the XB-42, replacing the piston engines of the XB-42 with two General Electric J35 engines of 4,000 lbf (17.8 kN) thrust each. Despite being the first American jet bomber to fly, it suffered stability issues and the design did not enter production.
The North American NA-40 was an American prototype bomber aircraft developed by North American Aviation in the late 1930s for evaluation by the United States Army Air Corps. Although unsuccessful, it led directly to the North American B-25 Mitchell medium bomber.
