Part VI. Redesigning: Why and how: Learning from earlier systems: When redesigning to correct flaws, add capabilities, or update aging features, figuring out what to keep and why is as important as knowing what to change

American Airlines was dissatisfied with the lumbering, uneconomical sleeper biplanes it flew on transcontinental routes in 1935. The company asked the Douglas Aircraft Co. to build a better transport. Douglas´s response was to take its DC-2 airliner, itself no bargain to operate on long flights, and widen the fuselage to accommodate 14 berths. What emerged was the DC-3, one of the most durable planes ever to fly.