[2] In 1934, the United States Army Air Corps requested for a twin-engine bomber with double the bomb load and range of the Martin B-10 then entering service.

While the Boeing design was clearly superior, the 299's four engines eliminated it from consideration despite being the favorite, and the crash of the prototype — caused by taking off with the controls still locked — put its purchase on hold.

During the depths of the Great Depression, the lower price of the DB-1 at $58,500 compared to $99,620 for the Model 299 also favored the Douglas entry, and it was ordered into immediate production in January 1936 as the B-18.

The wingspan was 4.5 ft (1.4 m) greater, the fuselage was narrower and deeper, and the wings were moved up to a mid-wing position to allow space under the spars for an enclosed bomb bay.

Added armament included manually operated nose, dorsal, and ventral gun turrets.

However, the B-18/B-18A's deficiencies were made apparent when an all-red Soviet Ilyushin TsKB-30 named Moskva (a prototype for the twin-engine DB-3 which flew the same year as the B-18) made a non-stop flight from Moscow to North America in April 1939, a distance of 4,970 mi (8,000 km), which was well beyond the capabilities of the B-18.

However, in spite of this, the B-18/B-18A was still the most numerous American bomber type deployed outside the continental United States at the time of the attack on Pearl Harbor.

When war came to the Pacific, most of the B-18/B-18A aircraft based overseas in the Philippines and in Hawaii were destroyed on the ground in the initial Japanese onslaught.

On 2 October 1942, a B-18A, piloted by Captain Howard Burhanna Jr. of the 99th Bomb Squadron, depth charged and sank the German submarine U-512 north of Cayenne, French Guiana.

[4] Two aircraft were transferred to the Brazilian Air Force in 1942, and were used with a provisional conversion training unit set up under the provisions of Lend-Lease.

Six B-18s are known to exist, five of them preserved or under restoration in museums in the United States, and one is a wreck still located at its crash site:[14] Data from McDonnell Douglas aircraft since 1920 : Volume I[24]General characteristics Performance Armament Avionics