The Federal Aviation Administration (FAA) is introducing new decision aid technology, called decision support tools (DSTs), into the air traffic control (ATC) workforce. Although considerable research has focused on the effects that DSTs will have on pilot-controller communications, relatively little research has been conducted on how DSTs will affect controller-controller communications. In this study, we examined the effects that aircraft density and different types of DSTs have on the communication exchanges occurring within en route ATC teams. Two hypotheses guided the research. Hypothesis 1: More communication exchanges will occur under high workload conditions, as compared with low workload conditions. Hypothesis 2: More communication exchanges will occur when using DSTs, as compared with not using DSTs.