Contrary to most sectors, to date the tourism and aviation industries have not managed to level off greenhouse gas emissions. Moreover, effective mitigation through technological innovation or structural and behavioural change cannot be expected shortly. Airlines and tourism companies appear to use carbon offsetting as a last resort. However, offsetting is generally acknowledged as a second-best solution for mitigating emissions, after reducing energy use. This paper seeks to determine the mitigation potential of voluntary carbon offsetting by comparing public and industry awareness of climate change and aviation emissions, and attitudes to various mitigation measures with relevant online communication by 64 offset providers. Methods were a literature review and online content analyses. Overall, the gaps that were identified between awareness, attitude and actual behaviour are not bridged by provider communication. From this perspective, the mitigation potential of voluntary carbon offsetting for achieving reductions of tourism transport emissions is estimated as low. The same conclusion is reached by comparing carbon dioxide volumes of flight offsets with actual air travel emissions. Current sales of flight offsets compensate less than 1% of all aviation emissions.