Experts excel on domain-relevant tasks in part because their knowledge supports comprehension and decisionmaking. However, few studies have examined the impact of expertise on both comprehension and decision-making. We investigated the impact of pilot expertise on understanding and making decisions about flight-related situations that varied in complexity. Expert pilots (airline and corporate) and novice pilots (General Aviation pilots with little commercial experience) read very brief scenarios that described simple or more complex situations during take-off, enroute, or approach phases of flights by complex commercial aircraft. Participants read each scenario at their own pace, discussed the problem in the scenario and how they would respond if they were pilot-in-command, rated the familiarity and difficulty of the described situation and answered questions about the scenario, and after reading all scenarios answered questions about appropriate solutions to the problem described in each scenario. Compared to the novices (N=28), the experts (N=37) rated the scenarios as more familiar and as less difficult, although both groups perceived the complex scenarios as less familiar and more difficult. The experts more accurately answered questions about the scenarios and made more accurate decisions about how to respond to the problems, although the more complex scenarios were remembered less accurately and prompted less accurate decisions overall. Experts also outperformed novices on a knowledge measure relevant to the decision-making task. The expertise effects were not moderated by scenario complexity. The findings suggest that domain-relevant knowledge facilitates comprehension of flight situations, as well as the ability to make decisions based on this comprehension.