Due to high implementation costs of the Next Generation Air Transportation System (NextGen) in the near-term, Air Traffic Controllers (ATCos) will have to manage mixed equipped airspace. Previous studies have evaluated different methods for training ATCos to use current-day tools and NextGen tools. More specifically, recent studies investigated how ATCo performance, workload, and situation awareness were affected by part-task and whole-task training. The current study builds on this research by examining ATCos' communication complexity as a function of these training types. Communication complexity is related to the number of commands ATCos incorporate in a single transmission, and it has been cited as a major contributor to incidents in aviation. The main finding of this investigation indicated that the largest differences in communication complexity between training groups occurred during the 100% NextGen equipped scenarios, with the whole-task group transmitting more complex communications than the part-task group.