Five complete planes were built just for testing, to answer questions like these: Could the wings bearing the 323-metric-ton craft at speeds of up to 600 miles per hour hold up to the stress?
更「奢侈」的，是設計成功之後，波音公司共製造了五架同型飛機，專做引擎、駕駛員操縱系統、自動導航系統和剎車器等各種實驗。譬如：重達三百廿三公噸的波音七四七，在每小時九百五十八公里的時速下飛行，機翼能否承受四﹘﹘六倍的大氣壓力？