A decision support tool, called Speed and Route Advisor (SARA), was developed at Schiphol Airport to help air traffic controllers achieve increased accuracy in traffic delivery. Its influence on controller performance, workload, and situation awareness was evaluated in a real-time simulation and in an operational trial. The findings indicate that this additional system support is necessary to achieve higher accuracy without increasing the controllers; workload. At the same time, controllers must stay in the loop to maintain situation awareness. This must be kept in mind while designing decision support systems such as SARA. © 2012 Taylor and Francis Group, LLC.