Developed from the UH-1 and following the Indian naming convention of the Bell helicopter series (before Cobra), the Model D255 'Iroquois Warrior' sought to develop a dedicated attack helicopter that was slim, maneuverable, and offered greater visibility and lower cost than existing designs. The initial mockup and the later stepped canopies, pictured below, illustrate the importance given to pilot field of view of the battlefield. The concept evolved into the Bell D262 and competed against the Lockheed AH-56 and Sikorsky Model S-66 for the 1964 Advanced Aerial Fire Support System contract. Bell lost and the D255 and D262 did not emerge from the mockup stage. However, the D255 would heavily influence the general configuration of the Bell Model 209 Cobra, which was developed inhouse with Bell money. After the AAFSS contract fell apart due to technical problems and political bickering, an interim attack platform was needed, and Bell responded with the 209.