AbstractDescribed are new methods of procurement, development and certification for complex aircraft systems and how these new methods have evolved over the past 15 years.The traditional methods of system design and equipment procurement that were used in the 1980's by aircraft manufacturers and that had been in place for decades, have undergone major changes following the aerospace recession of the late 80's and early 90's. Almost all of today's primes are procuring equipment at the system level and are requiring a more direct involvement by the supplier community in the design, development, integration, testing and certification of the aircraft as part of the system procurement contract. Furthermore, suppliers are being made accountable for the performance of the system in the field in terms of maintenance cost, equipment removal rates, and dispatchability.This paper describes the evolution process and some of the different approaches used by the prime community in the procurement of major aircraft systems. Comparisons are made using specific examples of fuel system procurement adopted by different aircraft manufacturers.Issues and benefits of these new methodologies are discussed and opportunities for improvements for the future are suggested.