Purpose This study investigated an appended belief-attitude-intention (BAI) model, which included two antecedent beliefs of attitude and two marketing factors as additional determinants of air traveller behavioural intentions towards low-cost airlines (LCAs). The hypothesized relationships were compared across different behaviouristic groups based on flying frequency, travel purpose and travel party size. Design/methodology/approach Survey data from 331 air travellers intercepted at a major international airport in Thailand were analysed using structural equation modelling and bootstrapping multiple-group comparisons to investigate the hypothesized mediation and moderation effects. Findings Results indicate that behavioural intention towards LCAs is largely influenced by perceived price, followed by attitude towards LCAs and subjective norm and not determined by airport accessibility. Antecedent beliefs of perceived service quality and uncertainty avoidance influence behavioural intention, as mediated by attitude towards LCAs. The role of subjective norm varied among air traveller groups. Practical implications Managers can manage price perceptions by focusing on LCA affordability and they should closely scrutinize these air traveller behaviouristic groups to identify opportunities to appeal to the distinctive cognitive responses of traveller segments. Originality/value This study tested an appended BAI model across three different air traveller behavioural characteristics, a multi-group analytical approach that can reveal meaningful implications, yet has been underused in LCA research.