Inexperienced and poorly trained Air Traffic Control Specialists (ATCSs) contribute to aircraft accidents and other serious aviation mishaps, which negatively impact human safety, the environment, government and personal property, and the efficient and smooth operation of the National Airspace System (NAS). The Federal Aviation Administration (FAA) can help remedy this problem by ensuring that ATCSs receive academic and simulator competency-based training. The purpose of this qualitative exploratory case study was to understand how ATCSs at an air traffic facility in the southeastern region of the United States (U.S.) described their experiences with the ATCoach simulation training (ATCoach) in developing job-related competencies. I employed Bloom et al.'s (1956) taxonomy of the cognitive domain and its six classifications (knowledge, comprehension, application, analysis, synthesis, and evaluation) to frame and align the study's research questions and interview questions to determine if five ATCSs perceived simulation as a valuable instructional method. Participants revealed that the ATCoach experiences is a valuable instructional method for enhancing ATC professionals' knowledge and skill levels by preparing them to transfer previous knowledge to practice in day-to-day ATC operations and improve their judgment, critical thinking, and decision-making skills - not their self-confidence. However, the simulator's physical fidelity limitations had an adverse influence on participants' learning experience. The findings, therefore, indicate ATC knowledge does not necessarily occur during the ATCoach but instead during previous classroom learning or experience. Future research should evaluate the entire ATC training program taking a learner from Certified Professional Controllers in Training (CPC-IT) status to Certified Professional Controllers (CPC). [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]