Following air traffic controller complaints, the FAA and NASA are reviewing changes to the software controlling the final approach spacing tool (FAST), one of the experimental Free Flight technologies being evaluated by the FAA (see story on page 110). FAST is designed to assign inbound aircraft to specific descent paths and runways to achieve a “balanced” flow at multi-runway airports. While FAST has improved throughput under normal weather conditions, controllers state that it cannot automatically accommodate major inbound routing changes during thunderstorms, or when re-routes are required outside its normal assignment limits. Pending software upgrades, FAST will be used as a controller situational awareness advisory tool.