Airports serve as more than simply ports of entry and exit for air travel. They have a significant impact on the configuration and functions of the cities they serve. As such, the timing of their construction is a key factor for cities to consider. The second Sydney airport is currently under construction in the west of the city at Badgerys Creek. This project was previously considered on two occasions: in 1971 and 1986. Primarily through modeling, this study explores the impacts on Sydney’s urban development, and subsequently other aspects of the city, that could have resulted if the airport had been built on one of these dates instead of 2014. The results indicate that the earliest date of construction for the airport presents the greatest potential for inducing urban development in its vicinity and improving accessibility, but also the greatest risk of being ineffective. In turn, the latest date provides the least potential for urban reconfiguration and accessibility gains but the lowest risk of being ineffective. It is clear that timing is an important factor to consider when planning the construction of an airport, however it should be considered in conjunction with the broader picture.