ABSTRACT Research on airline ads mainly investigated the effectiveness of verbal messages but not pictorial information. Previous research on mental imagery focused on each mental imagery dimension level the ad could generate instead of investigating the underlying path differences with different imagery-evoking level ads. Our study investigates the role each mental imagery dimension plays in people’s imagery processing process when exposed to varying levels of imagery-evoking airline visual ads. This research adopts a scenario-based experiment approach. A total of 246 scenario experiment surveys were collected in the UK. Participants were randomly allocated to one of the two real-world ads (imagery-evoking vs. less imagery-evoking). The findings are consistent with the elaboration likelihood model. When ad viewers process an imagery-evoking ad, the information processing is more elaborated. The vividness dimension plays a dominant role in the ad processing than the quantity dimension of mental imagery. The valence dimension of mental imagery mediates the relationship between vividness and purchase intention. When ad viewers process a less imagery-evoking airline ad, they rely on the quantity dimension for heuristics and the vividness dimension for relevant consumption information. The relationships between quantity and vividness dimensions of mental imagery on purchase intention are mediated by valence.