The business case for the Bombardier CSeries is sound. Although Bombardier is pursuing a narrow market segment, 100-149-seats, this is hardly an inconsequential market. There is an estimated market of more than 6,000 aircraft over 20 years, accounting for traffic growth and retirements/replacements. Airbus and Boeing are trending toward up-gauging their airplanes, which means largely abandoning this market segment to new competitors such as Bombardier and Embraer and potentially AVIC, Mitsubishi and Sukhoi.