美国的重型轰炸机B-17“飞行堡垒”在二战期间的问世之初曾被指责为“过分庞大”而输了选型竞标。 1934年8月6日,美国陆军航空兵发出了采购标书,要求开发装配多台发动机的轰炸机,并规定在一年的时间内出台原型机参加选型竞标。当时参加竞标的有波音公司、道格拉斯公司和马丁公司三家。波音公司分析:他们的竞争对手马丁公司和道格拉斯公司很可能用他们已有的双发飞机,通过改型来参加投标。为此,波音公司打算提出一个装配四台发动机的新型设计方案作为自己的主 The U.S. heavy bombers B-17 and Flight Fortress were accused of being “too bulky” at the beginning of World War II to lose their bidding. On August 6, 1934, the U.S. Army Aviation issued a bid for the procurement of bomber aircraft with multiple engines and stipulated that a prototype be put on bidding for the type selection within a year. At that time bidding there are Boeing, Douglas and Martin three companies. Boeing analysis: their rivals Martin and Douglas are likely to use their existing dual-engine aircraft, through the transformation to participate in the tender. To this end, Boeing intends to propose a new design with four engines as its own master