This paper analyzes the empirical relationship between market structure and price dispersion in the airline markets connecting the UK and the Republic of Ireland. Price dispersion is measured by a number of inequality indexes, calculated using fares posted on the Internet at specific days before takeoff. We find a negative correlation between market dominance and price dispersion; thus competition appears to hinder the airlines' ability to price discriminate to exploit consumers' heterogeneity in booking time preferences. Moreover, in the Christmas and Easter periods of high demand, fares are less dispersed, possibly because airlines target a less heterogenous set of consumers