NASA has developed a suite of tools that provide recommendations for rerouting aircraft while in enroute airspace when weather constraints do not develop as forecast. One of these tools, the Multi-Flight Common Routes tool (MFCR), has been designed to support traffic managers through the identification of a shared shorter route segment that can be assigned to a cluster of aircraft instead of assigning a unique reroute to each flight. A study using cognitive walkthroughs with 13 traffic managers and controllers was conducted to evaluate the functionality and use of MFCR. The results indicate that, if traffic managers take into consideration the weather and ensure that reroutes are ”well behaved” and work for sequencing and spacing, controllers view any extra workload as minor and acceptable, considering both the required rerouting and sequencing to be simply a part of their normal responsibilities. The results further provide a number of specific recommendations to extend the functions embedded in MFCR.