This article presents a study on the activities of the air traffic controllers of the Approach Control Area (APP) of Porto Alegre, Brazil, in different real scenarios. Based on interviews, questionnaires and the analysis of film of real scenes, the following were identified and analyzed: i) the perceptions of risk and complexity of the different air traffic scenes observed; ii) the cognitive factors (knowledge, strategy and attention dynamics) involved in the task and iii) the perception of the controller's workload. The results showed that the task complexity depends on the weather conditions, the number and type of aircraft in observation and that the controllers perceive the scenes in a similar way irrespective of their time in the profession and the type of control (radar or coordination). Attention is the cognitive factor with the greatest impact on the work and mental demand has the greatest impact on workload followed by time demand. The literature on the controllers work in Brazil is scarce and, therefore, this study aimed to contribute to the understanding of the work in one APP in order to promote future changes in the very problematic Brazilian air traffic system.