An important question from the viewpoint of competition analysis in the air transport industry is the extent to which low-cost airlines operating from a secondary airport compete with full-service airlines serving a main airport in a multiple airport region. In this paper we address the issue of the competition between full-service and low-cost airlines serving adjacent airports in the Greater London using econometric estimation of demand structure (own-and cross-price elasticities). Our analysis follows the methodology in (Pels, E., Nijkamp, P., Rietveld, P., 2000. Airport and airline competition for passengers departing from a large metropolitan area. Journal of Urban Economics, 48 (1), 29-45, Pels, E., Nijkamp, P., Rietveld, P., 2003. Access to and competition between airports: a case study for the San Francisco Bay area. Transportation Research Part A: Policy and Practice, 37 (1), 71-83). It is based on the nested logit model which we use to capture three key dimensions of passenger choice: air fare, surface-access costs and frequency. We obtained estimates of the own-and cross-price elasticities, which was the focus of our interest. On the basis of our understanding of the industry dynamics we find these estimates, especially of the cross-price elasticities, to be on the low side.