The usability assessment of software systems is becoming more relevant, especially when it comes to web-based systems. A well-built and user-friendly website is capable of capturing a potential customer. There are different methods to evaluate usability, including heuristic evaluation and usability testing with users. In the present work, the critical functionalities of an airline’s website were evaluated, such as the purchase of tickets, flight reservations, among others. First, a heuristic evaluation was performed and then a usability test with users. The evaluations were developed in an academic context and the participants were postgraduate students of a university. The problems detected in the first evaluation served to define specific tasks in the usability test with users. In this way, the results of the evaluations were complemented.