Some research suggests people are overconfident because of their personality characteristics, a lack of insight, or because overconfidence is beneficial in its own right (Dunning et al., 2003; Johnson & Fowler, 2011; Paulhus et al., 2003). But other research fits with the possibility that fluent experience in the moment can rapidly drive overconfidence (Alter and Oppenheimer, 2008). For example, fluency can push people to become overconfident in their ability to throw a dart, know how rainbows form or predict the future value of a commodity (Cardwell, Lindsay & Garry, 2017; Kardas and O’Brien, 2018; Newman et al., 2018). But surely there are limits to overconfidence. That is, even in the face of fluency manipulations known to increase feelings of confidence, reasonable people would reject the thought that they, for example, might be able to land a plane in an emergency or understand a foreign language. Across 11 experiments and 3529 subjects, we provide evidence supporting the idea that semantic context can rapidly increase people’s confidence in their ability to perform these highly specialised skills. In Part 1, we asked some people (but not others) to watch a trivially informative video of a pilot landing a plane before they rated their confidence in their own ability to land a plane. We found watching the video inflated people's confidence that they could land a plane. Moreover, we found people who watched the video were more confident in their ability to land the plane when they found the scenario easier to imagine. These findings fit with the idea that the semantic context of the video enables subjects to develop more detailed imaginations of themselves landing the plane, that they misconstrue as evidence that they could actually land the plane themselves. In Part 2, we found semantic context produced a similar illusion of ability when people were asked to evaluate their ability to apply foreign language abilities in new situations. We showed subjects a video clip of people speaking Danish either with, or without English subtitles. Then we asked subjects to rate how well they thought they would be able to understand Danish in new situations. Our results support the idea that semantic context boosts people’s confidence by making it easier to understand the situation at hand, but people then mistake that ease as evidence of their ability to comprehend Danish in novel situations. Our findings extend prior work by suggesting that increased semantic context creates illusions not just of prior experience or understanding—but also of the ability to actually do something implausible (Whittlesea, 1993; Cardwell, Lindsay & Garry, 2017).