The aviation sector is one of the fastest-growing segments of the transportation industry responsible for a considerable share of greenhouse gas emissions. Therefore, sustainability has become one of the central issues for the aviation sector. International regulatory bodies, airlines, and airport operators, along with aircraft manufacturers and suppliers have put forward initiatives to make aviation green. However, before the wider implementation of new sustainable practices, it is important to look at the opinion of passengers, as customers, on these matters. For this reason, this study aims to explore the knowledge and attitudes of Slovak passengers about green initiatives in aviation. The information about passengers’ knowledge and attitudes was collected through an online questionnaire. The data obtained from 514 respondents were evaluated employing descriptive and inferential statistics. From the results, several conclusions are apparent. Slovak passengers have generally weak environmental knowledge; therefore, it is important to provide them with enough relevant information to make informed decisions. The passengers have generally neutral to positive attitudes towards green initiatives in aviation, with the exception when these initiatives endanger their comfort or finances. For the development of green aviation, it is essential to increase the number of passengers with overall positive attitudes.