Urban systems are made up of city nodes and various kinds of interactions (social, economic, and political) that materialize to some extent through transportation and information flows (Meijers, 2005; Devriendt et al., 2010). Even though information and communication technologies (ICTs) overwhelmingly facilitate instant communication, face-to-face interactions are still important in the contemporary world (Bertolini and Dijst, 2003). High-speed physical means of transportation, such as airlines and high-speed railways (HSR), which can dramatically decrease the geographic and temporal constraints of commuting for business transactions, tourism, post-migratory travel to keep social links with friends and relatives, academic collaborations, and political activities, are all crucial in facilitating the formation of functional urban systems (Hall and Pain, 2006). Given their important role in linking urban areas,the development of airlines and HSR has been supported with substantial capital and infrastructure investment in China. The development of both systems has been very rapid. The global ranking of China’s airline transportation networks, based on scheduled seats, was 37th in 1978, but rose to second place after 2005. The number of civil-certificated schedule airports in mainland China increased from 94 in 1990 to 216 in 2016 and is expected to reach 260 in 2020, according to the 13th five-year plan of China’s contemporary transportation system (Fu et al., 2012; NDRC, 2016). Although China’s HSR networks entered the transportation market at a late stage in 2003, they have become the largest in the world (a total of 19,000 km by the end of 2015, accounting for over 60% of the global figure), even though HSR length per capita is less spectacular due to the size of the country (Delaplace and Dobruszkes, 2016). This network served > 70% of the population and the cities involved account for 80% of GDP (Wang et al., 2015; NDRC, 2016). It should be noticed that, in 2016 the mode shares of HSR and airlines are 6.4% and 2.6%, respectively, compared to the 81.2% and 1.4% of highways and waterways (NBSC, 2017). These investments have stimulated the integration of the national urban network (Ng and Wang, 2012) and are seen as part of its future integration with Euro-Asian urban systems via the by the Belt and Road Initiative (BRI) (Liu and Dunford, 2016).1 A great deal of the existing literature exploring the functional relationships within urban systems has relied upon scheduled seat airline data, measuring the capacity of aircraft movements across the world (Smith and Timberlake, 2001; Derudder and Witlox, 2005; Derudder and Witlox, 2009; Van Nuffel et al., 2010). However, HSR travel has received less attention, and also the few available studies on the functional relationships within urban systems in Europe (Hall and Pain, 2006) and China (Zhang et al., 2016) at the regional and sub-regional levels are based on time schedule data not a measure of capacity. In most of the research carried out to date, airline and HSR travel have been studied separately. One exception is the study by Xiao et al. (2013), in which passenger data of conventional railways and airlines are used to estimate a reversed gravity model to identify the attractiveness of a limited number of cities in China. Several studies have used the supply and demand side of airline flow data to understand HSR’s impacts on domestic aviation in China (Chen, 2017; Wang et al., 2017).