Technology has enabled advertisers to reach consumers at any number of moments within a purchase journey, and provided them with dozens of contextual signals to read. Digital marketing has naturally become hyper-rational. But human behaviour is often irrational - as behavioural economics has made clear. In order to design more relevant, more effective marketing we need to better understand how and why these irrational decisions are made. This research aims to leverage the latest thinking in behavioural economics, as well as primary research across flights, to better understand consumer decision-making and the role played by different media.