The entry of High-Speed Railways (HSR) represents a disruptive competition to airlines. Utilizing a unique dataset of all flights departing from Beijing to 113 domestic destinations in China since January 2009, we employ a difference-in-differences approach to examine the effects of HSR entry on on-time performance and to identify the channels. We document two main findings. First, the entry of HSR leads to significant reductions in the mean and variance of travel delays on the affected airline routes. Second, the reductions in departure delays and taxi-in time at the destination airports are identified as the main channels.