Willow Run B-24
The B-24 was produced in very large numbers. At nearly 19,000 units, with over 8,000 manufactured by Ford Motor Company, it holds the distinction of being the most produced heavy bomber in history, the most produced multi-engine aircraft in history and the most-produced American military aircraft.
This was 6 months BEFORE Pearl Harbor! Henry Ford was determined that he could mass produce bombers just as he had done with cars, so he built the Willow Run assembly plant in Michigan and proved it. It was the world's largest building under one roof at the time.
ONE B-24 every 55 minutes. . . and Ford had their own pilots to test them. They had no recalls.