3.1 The key challenge of the PPP is to provide a framework that enables NATS to secure the necessary investment for its business, while at the same time reducing the prices paid by its customers. This framework encompasses not just the Partnership itself, but also the arrangements for economic regulation through the Civil Aviation Authority. The key risk is that investment, to provide new systems and additional air traffic control capacity, will not be made. Figure 15 illustrates the virtuous circle of growth and investment that the Partnership must achieve.