Food waste is emerging as a global issue and has been recognised in the Sustainable Development Goals with a specific target to halve per capita global food waste at consumer levels and reduce food losses by 2030. Research on food waste has been neglected particularly in the aviation sector. The International Air Transport Association reported that 5.7 million tonnes of cabin waste was generated on airlines, up to 80.5% of which was leftover food and beverages. The exploration of passengers’ food wasting aims to provide insights for tackling the airline food waste problem. To address this issue, this research investigated the in-flight catering experience of 19 passengers from 21 full-service flights. Qualitative research techniques have been applied to analyse passengers’ food-wasting behaviour by collecting participant-produced photographs and completed questionnaires concerning food-related behaviour. This research identified key factors associated with passengers’ food wasting behaviour by adopting Design for Sustainable Behaviour approaches. Four types of factors were found to influence onboard passenger waste, these were normative, habitual, intentional and situational factors. This research indicates that behavioural change interventions need to incorporate the power of social norms to prevent food waste.