In this paper, I apply a difference-in-difference estimator to examine the impact of the merger between Iberia, Clickair and Vueling on route flight frequency, which is considered to be the main attribute of quality in the sector. Controlling for different indicators of competition and several route attributes, I show that the merger has implied a decrease in route flight frequency but the magnitude of this effect is modest. A plausible explanation of my result is a more collusive behavior of airlines offering flights in the routes affected by the merger.