# Research on the Relationship between Beijing-Tianjin-Hebei Airport Group and Regional Coordinated Development

Authors: Yafei Li; Meijun Teng; Yanjin Feng
Journal: Mathematical Problems in Engineering
 (2022)

---

## Abstract

The mutual development of airport groups and regions is gradually going global with the economic globalization. There is a contradiction between Beijing-Tianjin-Hebei (Jing-Jin-Ji) Airport Group and regional development, which leads to the unbalanced development of aviation enterprises in the region. Therefore, it is of major theoretical and practical significance to analyze the coordinated development relationship between Jing-Jin-Ji Airport Group and the region. This paper selects representative index system, establishes the adaptability evaluation model of airport group and regional development, and quantitatively analyzes the adaptability level of Jing-Jin-Ji Airport Group and radiation area. Taking New York Airport Group as a reference, the synergy degree between Jing-Jin-Ji Airport Group and the region is evaluated by the synergy evaluation model. Analyze the reasons for the development of New York Airport Group, and put forward the measures for the coordinated development of Jing-Jin-Ji Airport Group and the region in the future. The results show that the synergy index (SD) of Jing-Jin-Ji Airport Group is 0.5381, which is lower than that of New York Airport Group (0.7507), and Jing-Jin-Ji Airport Group is barely synergetic. It is necessary to optimize airspace, allocate flight resources, speed up the development of airport economy, and optimize the structure of airport groups. Jing-Jin-Ji Airport Group will be accelerated to enter a high-quality collaborative stage from the aspects of system and resource integration and government leadership.


---

## Body

## 1. Introduction

With the increasing trend of economic globalization, internationalization of economic factors, and optimization of industrial structure, the mutual development of airport groups and regions is gradually moving toward the whole world. Regional economic development needs the support of airport group, and the construction of airport group needs to be driven by regional development, which promotes the coordinated development of airport groups and regions. At the same time, as a way of external connection, air transportation has a pivotal influence on the development and construction of cities. Many foreign airport groups have been developed and perfected, such as London and New York Airport Group. Domestic airport group are also developing rapidly, but compared with the development of foreign airport group, the lack of reasonable division of labor between the airports in Jing-Jin-Ji Airport Group and the conflict with regional development have led to the development of aviation companies in the Beijing-Tianjin-Hebei region. In 2018, the passenger throughput and cargo and mail throughput of Beijing Capital Airport accounted for more than 75% of the total, which greatly inhibited the development of other airports in the same region. This is mainly caused by the unbalanced and uncoordinated development between the airport group and the region. The scale effect of airport group has been greatly restricted and cannot effectively drive the economic development of cities and regions. Therefore, how to better deploy the coordinated development of airport group and regions has become the focus of civil aviation industry and regional development. The completion and commissioning of Daxing Airport in 2019 will have a significant impact on Jing-Jin-Ji Airport Group. Jing-Jin-Ji Airport Group will meet the standards of two international large-scale hub airports, and the competition and cooperation relationship of the airport group will undergo earth-shaking changes. The development of its radiation area will also be greatly affected [1]. Therefore, analyzing the coordinated development relationship between Jing-Jin-Ji Airport Group and the region has important theoretical and practical significance.With the gradual diversification and complexity of airport operations, airport operations are no longer limited to a single transportation service. In addition, airports also have industrial functions, trade functions, and regional functions [2]. Researchers have conducted extensive and in-depth research on airport group and regional development. The American economic forecasting agency DRI-WEFT (1994) pointed out that air transportation will have an impact on regional city economy, industry, environment, etc. Generally, large hub airports will promote economic and social development, and flight delays will seriously affect the overall economic development level [3]. Bonnefoy et al. found that the development of European and American airport group is driven by low-cost airlines through data aggregation. With the existing airport infrastructure behind and the rapid increase in aircraft movements, Asian airport group have generated higher capacity demand [4]. Neufville proposed a dynamic strategy for the development of airport group in large metropolitan areas [5]. Tomoyuki Todoroki applied simulation to the research of multi-airport system and explored whether the multi-airport system can achieve better development under the competitive cooperation relationship [6].In terms of the research on the evaluation method of the relationship between the airport group and the regional coordinated development, Postorino and Praticò applied the multi-criteria decision-making (MCDM) method to the regional multi-airport system (MAS) to analyze the status of each airport in the system and study the airport’s performance changes [7]. Button and Taylor established a multiple nonlinear regression model and measured the impact of international air transportation on the regional economy and employment in the USA [8]. Skinner applies the disaggregated discrete choice model to the area of regional multi-airport system planning. By establishing a logit model, he analyzes the Washington area multi-airport system and studies the status of passengers choosing between Baltimore Airport, Dulles Airport, and National Airport [8]. Yang et al. proposed a convergence coefficient evaluation method, established a convergence model from the perspective of passenger capacity, and performed gradient positioning of each airport in the Pearl River Delta airport group, so as to avoid unnecessary route network competition and promote the coordinated development of airports in the airport group [9]. Chen and Li analyzed the coordinated development goals and reasonable development models of airport group by establishing theoretical models of air passengers’ behavioral mechanisms for different airports and then analyzed the coordinated development of airport group from the two levels of city clusters and metropolitan areas requirement [10]. Wang and Zhou took Nanjing Lukou International Airport as the main research object to study the coordination degree between its operational capabilities and regional economic and social development, use information entropy to objectively weight each indicator, and then construct a coupling coordination degree evaluation model [11]. Liu used entropy theory and general background method to study the adaptability of transportation industry and urban construction [12], Shi et al. and others used data envelopment analysis method and AHP method to evaluate the coordinated development degree of road investment and economic development [13], and Lei uses data envelopment analysis to study the coordination between the transportation industry and the social economy [14]. These methods use fewer indicators when analyzing the degree of coordination between airport group and regions, and cannot fully reflect the relationship between airport group and regional development. Based on the establishment of a complete indicator evaluation system, this study intends to adopt principal component analysis of indicators. A method is combined with regression analysis to study the relationship between airport group and regional coordinated development. The rapid development of Guangdong, China, is related to “city cluster + airport group” [15].In terms of the research on the evaluation method of the coordination degree of airport group, domestic and foreign scholars mostly adopt the evaluation model of the coordination degree. Neufville used dynamic planning strategies to guide the planning and layout of airport construction in the field of multi-airport systems, clarified the conceptual connotation and research scope of regional multi-airport systems, and summarized the common features of regional multi-airport systems [5]. Chen took the logistics development of the Beijing-Tianjin-Hebei region as the research object and used the coordination degree model to measure and study the coordination degree of the logistics development of Beijing-Tianjin-Hebei over the years. [16]. Xia established a Lotka–Volterra model between two airports to describe the changes in air passenger traffic and the resulting positive feedback effect on the changes in traffic during the competition between two airports [17]. Yang et al. calculated the comprehensive correlation degree and the synergy between systems based on the gray correlation analysis model and analyzed the Beijing-Tianjin-Hebei region as an example to evaluate whether the current coordinated development of airport group can effectively relieve Beijing’s noncapital functions [18]. Li constructed the evaluation system of the coordinated development level of the Central Plains Airport Group, using the Delphi method of analytic hierarchy process, standard deviation method, minimum relative information entropy principle comprehensive weighting method, and improved comprehensive coordination degree measurement model [19].Based on previous studies, this paper collects relevant data, establishes an index system, and uses adaptability evaluation model and coupling coordination model to study the coordination degree of airport group and regional development, and obtain the adaptability level of Beijing-Tianjin-Hebei (Jing-Jin-Ji) Airport Group and regional development, and the synergy level of airport group. On the basis of in-depth analysis of the reasons for the development of New York Airport Group, this paper puts forward the measures and means of coordinated development between Jing-Jin-Ji Airport Group and region in the future, with a view to promote the high-level benign development between Jing-Jin-Ji Airport Group and urban agglomeration, and providing research cases for the construction of airport group in China.


## 2. Methodology

### 2.1. Overview of the Study Area

At present, there are 10 civil aviation airports in the entire Beijing-Tianjin-Hebei region, 1 airport under construction, and 3 airports planned in the early stage. Because the throughput of airports in Beijing, Tianjin, and Shijiazhuang, Hebei, accounts for more than 90% of the throughput of the whole region, this paper mainly studies airports including Beijing Capital International Airport (PEK), Tianjin Binhai International Airport (TSN), and Shijiazhuang Zhengding International Airport (SJW).Development of Jing-Jin-JI Airport Group is obviously concentrated, with uneven distribution of resources. In 2018, the passenger throughput of PEK Airport was approximately 10.98 million passengers, while TSN Airport had only 23.59 million passengers and SJW Airport had only 11.33 million passengers. Among them, the difference between SJW Airport and PEK Airport is more than ten times. It can be seen that the development of small and medium airports is very lagging and internal differences are minimal, which affects the coordinated development of airport group and regions. With the launch of the “Implementation Opinions on Promoting the Coordinated Development of Civil Aviation in Beijing-Tianjin-Hebei” in 2017, the government plans to increase the international influence of the entire region and the airport group under the joint role of the region. It is also expected that the airports in the Beijing-Tianjin-Hebei region will achieve linkage and cooperation and complement each other’s advantages, and the air-rail combined transport for transportation will also be realized in 2030. The operation of Beijing Daxing International Airport (PKX) in 2019 will make Jing-Jin-Ji Airport Group greatly improved in terms of route layout, planning and development, and overall operational efficiency. Jing-Jin-Ji Airport Group will further form a close relationship with regional development and become a world-class airport group.


### 2.2. Data Sources and Research Ideas

In view of the difficulty of data acquisition, and the ten-year study on airport group and regional development, this paper selects the original data of Jing-Jin-Ji Airport Group from 2009 to 2018. Among them, airport group data come from “Statistical Data on Civil Aviation of China,” and regional development data come from “National Bureau of Statistics,” as shown in Tables1 and 2. In order to study the coordinated development level of Jing-Jin-Ji Airport Group compared with the international mature airport group, this study also collected relevant development data of Jing-Jin-Ji Airport Group and New York Airport Group, as shown in Table 3.Table 1
Raw data of Jing-Jin-Ji Airport Group.
YearAnnual cargo and mail throughputAnnual passenger throughputAnnual movements2009166.243227247.521759.55152010177.966558394.881665.45842011185.631769024.985267.292012203.37656819492.141169.55062013212.7164659885.872472.04662014212.71646510380.237175.27252015215.14125511023.87677.2622016222.401012911847.993381.8592017236.208507713233.85488.86762018240.400814241.99692.7621Table 2
Raw data of regional development.
YearPer capita disposable income (RMB)Regional GDP (100 million yuan)Receiving foreign tourists (million person-times)Number of employed persons in the air transport industryYear-end resident populationTotal import and export (100 million US dollars)Foreign exchange income from international tourism (millions of dollars)20092095336910640327101231993.9584720102321043732843120104552643.6681520112603952075762806106143251.3761920122888057348771568107713338792020132746062686678195109193563.8797220142998966479682283110523818813420153262369359686014110923299.8840520163544375625689598112053042.99197201738579825606967871124748689460201841256851396102584112705889.57273Table 3
Original data of Jing-Jin-Ji Airport Group and New York Airport Group development in 2018.
Primary indexSecondary indexJing-Jin-Ji Airport GroupNew York Airport GroupRoute network indicatorsDaily average flight density (freight)13201798Domestic and international navigation points (number)443501International passenger transfer rate (%)16.236Air transport scale indicatorsTotal annual passenger throughput (10,000 passengers)1424119652Total annual cargo and mail throughput (10,000 tons)240202Annual total number of takeoffs and landings (ten thousand)93126Traffic convenience indexThe diversity of airport public transportation options (types)2.24.8Distance from airport to city (km)2724.7Airport service-level indexAverage delay time (min)30.228.2Airport departure flight punctuality rate (%)70.8369.34In this paper, a relatively complete index of coordinated development of airport groups and regions is selected, and the adaptability evaluation method is adopted to quantitatively analyze the adaptability level of Jing-Jin-Ji Airport Group and region. The coordinated development level of Jing-Jin-Ji Airport Group is studied by the method of coordination degree evaluation and compared with the international mature airport group (New York Airport Group).


### 2.3. Research on Adaptability Evaluation of Airport Group and City Cluster

Adaptability refers to the level of coordination between two things that interact in terms of development level and service capability. This paper discusses the adaptation and coordination degree of airport group construction and development to regional economic development, urban construction, external demand, and various development indicators.


#### 2.3.1. Construction of the Evaluation Index System for Airport Group and Regional Adaptability

The selection of indicators for Jing-Jin-Ji Airport Group should take into account the indicators that can best affect the development status and can also predict the future sustainable development, that is, the indicators that can be applied to future development while taking into account the development level over the years. The data that best reflect the operational status of an airport are annual passenger throughput, annual cargo and mail throughput, and annual takeoffs and landings. These three directly reflect the scale effect of an airport. The selection of regional indicators needs to take into account the three major regional development indicators, economic society and industry, specific to residents’ living standards, external demand, import and export economy, talent employment, and factors that have a direct impact on the airport group (Figure1). The selection indicators are as follows:Figure 1
Airport group and regional adaptability evaluation index.In the airport group and regional adaptability evaluation index system, the route network index reflects the density of the route network of the airport group, the construction level of the central hub, and the coverage. The scale of air transportation reflects the airport’s cargo and passenger transportation capacity and the airport’s operating scale. Traffic convenience reflects the ability of the entire airport to connect and interact with regional urban agglomerations, as well as the degree of flexible connection with other intra-city traffic. The service level of the airport reflects the operation efficiency and processing capacity of the airport.


#### 2.3.2. Steps to Evaluate the Suitability of Airport Group and Regions

Standardize the original data, and scale the data to make the result more accurate. The Z-score standardization method [20] is used here, and the following information needs to be obtained: original data (xi), mean value (x¯), standard deviation (s), and standard value (x∗), and these are substituted into the Z-score formula, which is(1)x∗=xi−x¯s.Calculate the correlation coefficient, and the formula is as follows:(2)xij∑k=1nxki−xi¯xkj−xj¯∑k=1nxki−xi¯2∑k=1nxkj−xj¯2.Arrange the correlation coefficients in a matrix:(3)R=r11⋯r1p⋮⋱⋮rp1⋯rpp.Calculate the characteristic rootλ and the characteristic vector e, solve |λE-E| = 0 to find the characteristic root λ, and sort λ1 from large to small. Find the eigenvector ei so that ‖ei‖ = 1.Calculate the cumulative variance contribution rateα and the score F:(4)α=∑i=1pαi.Among them,αi is the variance contribution rate, and p is the number of indicators.(5)αi=λi∑k=1pλk,(6)F=∑i=1mαieix∗.Calculate the firstm principal components (the contribution rate is greater than 85%) to get the final score, solve the linear regression equation, find the coordination value of the subsystem, and finally calculate the overall state coordination [21].(1)
The degree of state coordination required by systemj to system i:(7)Aij=expXi−X12s.(2)
The degree of state coordination required by systemi to system j:(8)Aji=expYi−Y12s.(3)
The formula of the mutual coordination degreeCs(i, j) between i and j is as follows:(9)Csi,j=minAij,AjimaxAij,Aji,0<Csi,j<1.DivideCs(i, j) into four levels: Table 4.Table 4
Mutual coordination level.
Cs (i, j)≤0.50.5～0.70.7～0.9≥0.9RankTotally uncoordinatedUncoordinatedMedium-coordinatedCoordinated


### 2.4. Research on Evaluation of Synergy of Airport Group

#### 2.4.1. Construction of the Evaluation Index System for the Coordination Degree of the Airport Group

Coupling coordination degree model (CCDM) [22] is used to analyze the coordinated development level of things. Coupling degree refers to the dynamic relationship between two or more systems, which influences each other and realizes coordinated development. Yuanyuan Yang established the evaluation index system of rural production and living ecological function in Beijing-Tianjin-Hebei (BTH) region and used the coupling coordination degree model (CCDM) to explore the spatial and temporal characteristics of the coupling and coordination relationship of the three basic rural functions in the study area from 2000 to 2015 [23].This research is based on the coupling coordination degree model and analyzes the coordinated development level of Jing-Jin-Ji Airport Group by comparing different airport groups. New York Airport Group is the benchmark for the development of the global airport group, and its level of coordinated development with surrounding areas is very high. Taking New York Airport Group as a reference, this study analyzes the synergy degree between Jing-Jin-Ji Airport Group and New York Airport Group, so as to judge the synergy development level of Jing-Jin-Ji Airport Group and obtain the existing synergy development level and suggestions of Jing-Jin-Ji Airport Group more intuitively.This study selects research indicators from four aspects. The biggest impact on the airport group is the part of its route network, and the opening of waypoints, the degree of airspace congestion, the seat factor, and the primacy of the airport all affect the efficiency of airport flights. The annual passenger throughput, annual cargo and mail throughput, and the number of takeoffs and landings of an airport directly affect the overall efficiency of an airport. From the perspective of the internal impact of the airport, the service quality of the airport (such as delay time and flight punctuality) also directly affects the operating efficiency of the airport. From an external analysis point of view, the airport itself and the surrounding traffic environment indirectly affect the development of the airport and the airport group, such as the distance between the airport and the city and the diversity of residents’ travel options. In summary, in view of the characteristics of the synergy of the airport group, we select the following indicator system (Figure2).Figure 2
Evaluation index system for the coordination degree of the airport group.In the evaluation index system for the coordination degree of the airport group, the route network index reflects the density of the route network of the airport group, the construction level of the central hub, and the coverage. The scale of air transportation reflects the airport’s cargo and passenger transportation capacity and the airport’s operating scale. Traffic convenience reflects the ability of the entire airport to connect and interact with regional urban agglomerations, as well as the degree of flexible connection with other intra-city traffic. The service level of the airport reflects the operation efficiency and processing capacity of the airport.


#### 2.4.2. Evaluation Steps of Synergy of Airport Group

Based on the coupling coordination degree model (CCDM) [22–24], this study evaluates the degree of coordinated development of airport group. The specific steps are as follows:(1)
Coupling degree SC(10)Sc=c1×c2×c3×c4c1+c2+c3+c4/44p.Among them,p is the adjustment coefficient, usually p ≥ 4, where p takes the value of 4, and C1, C2, C3, and C4 are the development degrees of the first-level indicators, respectively.(11)CI=∑j=1kwji×xji.Among them,xji represents the original data or data standardized by the original data, and wji represents the weight of the jth second-level index corresponding to the ith first-level index.(2)
Comprehensive evaluation index T(12)T=αC1+βC2+ηC3+λC4.Among them,α, β, η, and λ are the weights of the first-level indicators.(3)
Coordination degree SD(13)SD=SC×T.Usually SD is not greater than 1. According to the connotation of coordinated development of airport group, the synergy level is divided.This study will use the expert scoring method and the entropy weight method to calculate the primary and secondary indicators of CCDM, respectively. The calculation process of the entropy weight method is as follows, and the entropy value calculation formula of the jth indicator is(14)ej=−1lnn∑i=1npijlnpij.Coefficient of difference:(15)dj=1−ej,(16)wj=dj∑i=1ndi.After calculating the weights of the first-level indicators and the second-level indicators, the comprehensive weights of the indicators are calculated.


### 2.5. Comprehensive Evaluation Method of the Relationship between Airport Group and Regional Coordinated Development

In order to analyze the relationship between Jing-Jin-Ji Airport Group and the regional coordinated development in a more in-depth manner, this paper uses a method that combines adaptability evaluation and synergy evaluation. Among them, the adaptability evaluation of the airport group and the region is used to reflect the development service level of the airport and the coupling degree of the regional economic development, and the evaluation of coordination degree is to compare the synergy level of Jing-Jin-Ji Airport Group with that of New York Airport Group to judge whether Jing-Jin-Ji Airport Group has reached the stage of high-quality coordinated development. Integrating the two evaluation results, we finally get the level of coordinated development of airport group and regions, as shown in Table5.Table 5
Airport group and regional coordinated development level.
Evaluation result valueAirport group and regional coordination levelCoordination levelHigh-quality synergyLowNoUncoordinatedLowYesUncoordinatedHighNoLow-level coordinationHighYesHigh-level coordination


## 2.1. Overview of the Study Area

At present, there are 10 civil aviation airports in the entire Beijing-Tianjin-Hebei region, 1 airport under construction, and 3 airports planned in the early stage. Because the throughput of airports in Beijing, Tianjin, and Shijiazhuang, Hebei, accounts for more than 90% of the throughput of the whole region, this paper mainly studies airports including Beijing Capital International Airport (PEK), Tianjin Binhai International Airport (TSN), and Shijiazhuang Zhengding International Airport (SJW).Development of Jing-Jin-JI Airport Group is obviously concentrated, with uneven distribution of resources. In 2018, the passenger throughput of PEK Airport was approximately 10.98 million passengers, while TSN Airport had only 23.59 million passengers and SJW Airport had only 11.33 million passengers. Among them, the difference between SJW Airport and PEK Airport is more than ten times. It can be seen that the development of small and medium airports is very lagging and internal differences are minimal, which affects the coordinated development of airport group and regions. With the launch of the “Implementation Opinions on Promoting the Coordinated Development of Civil Aviation in Beijing-Tianjin-Hebei” in 2017, the government plans to increase the international influence of the entire region and the airport group under the joint role of the region. It is also expected that the airports in the Beijing-Tianjin-Hebei region will achieve linkage and cooperation and complement each other’s advantages, and the air-rail combined transport for transportation will also be realized in 2030. The operation of Beijing Daxing International Airport (PKX) in 2019 will make Jing-Jin-Ji Airport Group greatly improved in terms of route layout, planning and development, and overall operational efficiency. Jing-Jin-Ji Airport Group will further form a close relationship with regional development and become a world-class airport group.


## 2.2. Data Sources and Research Ideas

In view of the difficulty of data acquisition, and the ten-year study on airport group and regional development, this paper selects the original data of Jing-Jin-Ji Airport Group from 2009 to 2018. Among them, airport group data come from “Statistical Data on Civil Aviation of China,” and regional development data come from “National Bureau of Statistics,” as shown in Tables1 and 2. In order to study the coordinated development level of Jing-Jin-Ji Airport Group compared with the international mature airport group, this study also collected relevant development data of Jing-Jin-Ji Airport Group and New York Airport Group, as shown in Table 3.Table 1
Raw data of Jing-Jin-Ji Airport Group.
YearAnnual cargo and mail throughputAnnual passenger throughputAnnual movements2009166.243227247.521759.55152010177.966558394.881665.45842011185.631769024.985267.292012203.37656819492.141169.55062013212.7164659885.872472.04662014212.71646510380.237175.27252015215.14125511023.87677.2622016222.401012911847.993381.8592017236.208507713233.85488.86762018240.400814241.99692.7621Table 2
Raw data of regional development.
YearPer capita disposable income (RMB)Regional GDP (100 million yuan)Receiving foreign tourists (million person-times)Number of employed persons in the air transport industryYear-end resident populationTotal import and export (100 million US dollars)Foreign exchange income from international tourism (millions of dollars)20092095336910640327101231993.9584720102321043732843120104552643.6681520112603952075762806106143251.3761920122888057348771568107713338792020132746062686678195109193563.8797220142998966479682283110523818813420153262369359686014110923299.8840520163544375625689598112053042.99197201738579825606967871124748689460201841256851396102584112705889.57273Table 3
Original data of Jing-Jin-Ji Airport Group and New York Airport Group development in 2018.
Primary indexSecondary indexJing-Jin-Ji Airport GroupNew York Airport GroupRoute network indicatorsDaily average flight density (freight)13201798Domestic and international navigation points (number)443501International passenger transfer rate (%)16.236Air transport scale indicatorsTotal annual passenger throughput (10,000 passengers)1424119652Total annual cargo and mail throughput (10,000 tons)240202Annual total number of takeoffs and landings (ten thousand)93126Traffic convenience indexThe diversity of airport public transportation options (types)2.24.8Distance from airport to city (km)2724.7Airport service-level indexAverage delay time (min)30.228.2Airport departure flight punctuality rate (%)70.8369.34In this paper, a relatively complete index of coordinated development of airport groups and regions is selected, and the adaptability evaluation method is adopted to quantitatively analyze the adaptability level of Jing-Jin-Ji Airport Group and region. The coordinated development level of Jing-Jin-Ji Airport Group is studied by the method of coordination degree evaluation and compared with the international mature airport group (New York Airport Group).


## 2.3. Research on Adaptability Evaluation of Airport Group and City Cluster

Adaptability refers to the level of coordination between two things that interact in terms of development level and service capability. This paper discusses the adaptation and coordination degree of airport group construction and development to regional economic development, urban construction, external demand, and various development indicators.


### 2.3.1. Construction of the Evaluation Index System for Airport Group and Regional Adaptability

The selection of indicators for Jing-Jin-Ji Airport Group should take into account the indicators that can best affect the development status and can also predict the future sustainable development, that is, the indicators that can be applied to future development while taking into account the development level over the years. The data that best reflect the operational status of an airport are annual passenger throughput, annual cargo and mail throughput, and annual takeoffs and landings. These three directly reflect the scale effect of an airport. The selection of regional indicators needs to take into account the three major regional development indicators, economic society and industry, specific to residents’ living standards, external demand, import and export economy, talent employment, and factors that have a direct impact on the airport group (Figure1). The selection indicators are as follows:Figure 1
Airport group and regional adaptability evaluation index.In the airport group and regional adaptability evaluation index system, the route network index reflects the density of the route network of the airport group, the construction level of the central hub, and the coverage. The scale of air transportation reflects the airport’s cargo and passenger transportation capacity and the airport’s operating scale. Traffic convenience reflects the ability of the entire airport to connect and interact with regional urban agglomerations, as well as the degree of flexible connection with other intra-city traffic. The service level of the airport reflects the operation efficiency and processing capacity of the airport.


### 2.3.2. Steps to Evaluate the Suitability of Airport Group and Regions

Standardize the original data, and scale the data to make the result more accurate. The Z-score standardization method [20] is used here, and the following information needs to be obtained: original data (xi), mean value (x¯), standard deviation (s), and standard value (x∗), and these are substituted into the Z-score formula, which is(1)x∗=xi−x¯s.Calculate the correlation coefficient, and the formula is as follows:(2)xij∑k=1nxki−xi¯xkj−xj¯∑k=1nxki−xi¯2∑k=1nxkj−xj¯2.Arrange the correlation coefficients in a matrix:(3)R=r11⋯r1p⋮⋱⋮rp1⋯rpp.Calculate the characteristic rootλ and the characteristic vector e, solve |λE-E| = 0 to find the characteristic root λ, and sort λ1 from large to small. Find the eigenvector ei so that ‖ei‖ = 1.Calculate the cumulative variance contribution rateα and the score F:(4)α=∑i=1pαi.Among them,αi is the variance contribution rate, and p is the number of indicators.(5)αi=λi∑k=1pλk,(6)F=∑i=1mαieix∗.Calculate the firstm principal components (the contribution rate is greater than 85%) to get the final score, solve the linear regression equation, find the coordination value of the subsystem, and finally calculate the overall state coordination [21].(1)
The degree of state coordination required by systemj to system i:(7)Aij=expXi−X12s.(2)
The degree of state coordination required by systemi to system j:(8)Aji=expYi−Y12s.(3)
The formula of the mutual coordination degreeCs(i, j) between i and j is as follows:(9)Csi,j=minAij,AjimaxAij,Aji,0<Csi,j<1.DivideCs(i, j) into four levels: Table 4.Table 4
Mutual coordination level.
Cs (i, j)≤0.50.5～0.70.7～0.9≥0.9RankTotally uncoordinatedUncoordinatedMedium-coordinatedCoordinated


## 2.3.1. Construction of the Evaluation Index System for Airport Group and Regional Adaptability

The selection of indicators for Jing-Jin-Ji Airport Group should take into account the indicators that can best affect the development status and can also predict the future sustainable development, that is, the indicators that can be applied to future development while taking into account the development level over the years. The data that best reflect the operational status of an airport are annual passenger throughput, annual cargo and mail throughput, and annual takeoffs and landings. These three directly reflect the scale effect of an airport. The selection of regional indicators needs to take into account the three major regional development indicators, economic society and industry, specific to residents’ living standards, external demand, import and export economy, talent employment, and factors that have a direct impact on the airport group (Figure1). The selection indicators are as follows:Figure 1
Airport group and regional adaptability evaluation index.In the airport group and regional adaptability evaluation index system, the route network index reflects the density of the route network of the airport group, the construction level of the central hub, and the coverage. The scale of air transportation reflects the airport’s cargo and passenger transportation capacity and the airport’s operating scale. Traffic convenience reflects the ability of the entire airport to connect and interact with regional urban agglomerations, as well as the degree of flexible connection with other intra-city traffic. The service level of the airport reflects the operation efficiency and processing capacity of the airport.


## 2.3.2. Steps to Evaluate the Suitability of Airport Group and Regions

Standardize the original data, and scale the data to make the result more accurate. The Z-score standardization method [20] is used here, and the following information needs to be obtained: original data (xi), mean value (x¯), standard deviation (s), and standard value (x∗), and these are substituted into the Z-score formula, which is(1)x∗=xi−x¯s.Calculate the correlation coefficient, and the formula is as follows:(2)xij∑k=1nxki−xi¯xkj−xj¯∑k=1nxki−xi¯2∑k=1nxkj−xj¯2.Arrange the correlation coefficients in a matrix:(3)R=r11⋯r1p⋮⋱⋮rp1⋯rpp.Calculate the characteristic rootλ and the characteristic vector e, solve |λE-E| = 0 to find the characteristic root λ, and sort λ1 from large to small. Find the eigenvector ei so that ‖ei‖ = 1.Calculate the cumulative variance contribution rateα and the score F:(4)α=∑i=1pαi.Among them,αi is the variance contribution rate, and p is the number of indicators.(5)αi=λi∑k=1pλk,(6)F=∑i=1mαieix∗.Calculate the firstm principal components (the contribution rate is greater than 85%) to get the final score, solve the linear regression equation, find the coordination value of the subsystem, and finally calculate the overall state coordination [21].(1)
The degree of state coordination required by systemj to system i:(7)Aij=expXi−X12s.(2)
The degree of state coordination required by systemi to system j:(8)Aji=expYi−Y12s.(3)
The formula of the mutual coordination degreeCs(i, j) between i and j is as follows:(9)Csi,j=minAij,AjimaxAij,Aji,0<Csi,j<1.DivideCs(i, j) into four levels: Table 4.Table 4
Mutual coordination level.
Cs (i, j)≤0.50.5～0.70.7～0.9≥0.9RankTotally uncoordinatedUncoordinatedMedium-coordinatedCoordinated


## 2.4. Research on Evaluation of Synergy of Airport Group

### 2.4.1. Construction of the Evaluation Index System for the Coordination Degree of the Airport Group

Coupling coordination degree model (CCDM) [22] is used to analyze the coordinated development level of things. Coupling degree refers to the dynamic relationship between two or more systems, which influences each other and realizes coordinated development. Yuanyuan Yang established the evaluation index system of rural production and living ecological function in Beijing-Tianjin-Hebei (BTH) region and used the coupling coordination degree model (CCDM) to explore the spatial and temporal characteristics of the coupling and coordination relationship of the three basic rural functions in the study area from 2000 to 2015 [23].This research is based on the coupling coordination degree model and analyzes the coordinated development level of Jing-Jin-Ji Airport Group by comparing different airport groups. New York Airport Group is the benchmark for the development of the global airport group, and its level of coordinated development with surrounding areas is very high. Taking New York Airport Group as a reference, this study analyzes the synergy degree between Jing-Jin-Ji Airport Group and New York Airport Group, so as to judge the synergy development level of Jing-Jin-Ji Airport Group and obtain the existing synergy development level and suggestions of Jing-Jin-Ji Airport Group more intuitively.This study selects research indicators from four aspects. The biggest impact on the airport group is the part of its route network, and the opening of waypoints, the degree of airspace congestion, the seat factor, and the primacy of the airport all affect the efficiency of airport flights. The annual passenger throughput, annual cargo and mail throughput, and the number of takeoffs and landings of an airport directly affect the overall efficiency of an airport. From the perspective of the internal impact of the airport, the service quality of the airport (such as delay time and flight punctuality) also directly affects the operating efficiency of the airport. From an external analysis point of view, the airport itself and the surrounding traffic environment indirectly affect the development of the airport and the airport group, such as the distance between the airport and the city and the diversity of residents’ travel options. In summary, in view of the characteristics of the synergy of the airport group, we select the following indicator system (Figure2).Figure 2
Evaluation index system for the coordination degree of the airport group.In the evaluation index system for the coordination degree of the airport group, the route network index reflects the density of the route network of the airport group, the construction level of the central hub, and the coverage. The scale of air transportation reflects the airport’s cargo and passenger transportation capacity and the airport’s operating scale. Traffic convenience reflects the ability of the entire airport to connect and interact with regional urban agglomerations, as well as the degree of flexible connection with other intra-city traffic. The service level of the airport reflects the operation efficiency and processing capacity of the airport.


### 2.4.2. Evaluation Steps of Synergy of Airport Group

Based on the coupling coordination degree model (CCDM) [22–24], this study evaluates the degree of coordinated development of airport group. The specific steps are as follows:(1)
Coupling degree SC(10)Sc=c1×c2×c3×c4c1+c2+c3+c4/44p.Among them,p is the adjustment coefficient, usually p ≥ 4, where p takes the value of 4, and C1, C2, C3, and C4 are the development degrees of the first-level indicators, respectively.(11)CI=∑j=1kwji×xji.Among them,xji represents the original data or data standardized by the original data, and wji represents the weight of the jth second-level index corresponding to the ith first-level index.(2)
Comprehensive evaluation index T(12)T=αC1+βC2+ηC3+λC4.Among them,α, β, η, and λ are the weights of the first-level indicators.(3)
Coordination degree SD(13)SD=SC×T.Usually SD is not greater than 1. According to the connotation of coordinated development of airport group, the synergy level is divided.This study will use the expert scoring method and the entropy weight method to calculate the primary and secondary indicators of CCDM, respectively. The calculation process of the entropy weight method is as follows, and the entropy value calculation formula of the jth indicator is(14)ej=−1lnn∑i=1npijlnpij.Coefficient of difference:(15)dj=1−ej,(16)wj=dj∑i=1ndi.After calculating the weights of the first-level indicators and the second-level indicators, the comprehensive weights of the indicators are calculated.


## 2.4.1. Construction of the Evaluation Index System for the Coordination Degree of the Airport Group

Coupling coordination degree model (CCDM) [22] is used to analyze the coordinated development level of things. Coupling degree refers to the dynamic relationship between two or more systems, which influences each other and realizes coordinated development. Yuanyuan Yang established the evaluation index system of rural production and living ecological function in Beijing-Tianjin-Hebei (BTH) region and used the coupling coordination degree model (CCDM) to explore the spatial and temporal characteristics of the coupling and coordination relationship of the three basic rural functions in the study area from 2000 to 2015 [23].This research is based on the coupling coordination degree model and analyzes the coordinated development level of Jing-Jin-Ji Airport Group by comparing different airport groups. New York Airport Group is the benchmark for the development of the global airport group, and its level of coordinated development with surrounding areas is very high. Taking New York Airport Group as a reference, this study analyzes the synergy degree between Jing-Jin-Ji Airport Group and New York Airport Group, so as to judge the synergy development level of Jing-Jin-Ji Airport Group and obtain the existing synergy development level and suggestions of Jing-Jin-Ji Airport Group more intuitively.This study selects research indicators from four aspects. The biggest impact on the airport group is the part of its route network, and the opening of waypoints, the degree of airspace congestion, the seat factor, and the primacy of the airport all affect the efficiency of airport flights. The annual passenger throughput, annual cargo and mail throughput, and the number of takeoffs and landings of an airport directly affect the overall efficiency of an airport. From the perspective of the internal impact of the airport, the service quality of the airport (such as delay time and flight punctuality) also directly affects the operating efficiency of the airport. From an external analysis point of view, the airport itself and the surrounding traffic environment indirectly affect the development of the airport and the airport group, such as the distance between the airport and the city and the diversity of residents’ travel options. In summary, in view of the characteristics of the synergy of the airport group, we select the following indicator system (Figure2).Figure 2
Evaluation index system for the coordination degree of the airport group.In the evaluation index system for the coordination degree of the airport group, the route network index reflects the density of the route network of the airport group, the construction level of the central hub, and the coverage. The scale of air transportation reflects the airport’s cargo and passenger transportation capacity and the airport’s operating scale. Traffic convenience reflects the ability of the entire airport to connect and interact with regional urban agglomerations, as well as the degree of flexible connection with other intra-city traffic. The service level of the airport reflects the operation efficiency and processing capacity of the airport.


## 2.4.2. Evaluation Steps of Synergy of Airport Group

Based on the coupling coordination degree model (CCDM) [22–24], this study evaluates the degree of coordinated development of airport group. The specific steps are as follows:(1)
Coupling degree SC(10)Sc=c1×c2×c3×c4c1+c2+c3+c4/44p.Among them,p is the adjustment coefficient, usually p ≥ 4, where p takes the value of 4, and C1, C2, C3, and C4 are the development degrees of the first-level indicators, respectively.(11)CI=∑j=1kwji×xji.Among them,xji represents the original data or data standardized by the original data, and wji represents the weight of the jth second-level index corresponding to the ith first-level index.(2)
Comprehensive evaluation index T(12)T=αC1+βC2+ηC3+λC4.Among them,α, β, η, and λ are the weights of the first-level indicators.(3)
Coordination degree SD(13)SD=SC×T.Usually SD is not greater than 1. According to the connotation of coordinated development of airport group, the synergy level is divided.This study will use the expert scoring method and the entropy weight method to calculate the primary and secondary indicators of CCDM, respectively. The calculation process of the entropy weight method is as follows, and the entropy value calculation formula of the jth indicator is(14)ej=−1lnn∑i=1npijlnpij.Coefficient of difference:(15)dj=1−ej,(16)wj=dj∑i=1ndi.After calculating the weights of the first-level indicators and the second-level indicators, the comprehensive weights of the indicators are calculated.


## 2.5. Comprehensive Evaluation Method of the Relationship between Airport Group and Regional Coordinated Development

In order to analyze the relationship between Jing-Jin-Ji Airport Group and the regional coordinated development in a more in-depth manner, this paper uses a method that combines adaptability evaluation and synergy evaluation. Among them, the adaptability evaluation of the airport group and the region is used to reflect the development service level of the airport and the coupling degree of the regional economic development, and the evaluation of coordination degree is to compare the synergy level of Jing-Jin-Ji Airport Group with that of New York Airport Group to judge whether Jing-Jin-Ji Airport Group has reached the stage of high-quality coordinated development. Integrating the two evaluation results, we finally get the level of coordinated development of airport group and regions, as shown in Table5.Table 5
Airport group and regional coordinated development level.
Evaluation result valueAirport group and regional coordination levelCoordination levelHigh-quality synergyLowNoUncoordinatedLowYesUncoordinatedHighNoLow-level coordinationHighYesHigh-level coordination


## 3. Results and Discussions

### 3.1. Evaluation Results of Jing-Jin-Ji Airport Group and Regional Adaptability

In this study, SPSS (Statistical Product and Service Solutions) software was used for factor analysis. SPSS is a series of software products launched by IBM for statistical analysis, data mining, predictive analysis, and decision support. The comprehensive scores of the index factors of Jing-Jin-Ji Airport Group and the region were obtained. The data were standardized according to formula (1), and each index factor was calculated according to formulas (4)-(5). The comprehensive scores are shown in Table 6 and Figures 3 and 4.Table 6
Comprehensive scores of Jing-Jin-Ji Airport Group subsystem and regional subsystem.
YearComprehensive score of airport group subsystem iComprehensive score of regional subsystem j2009−1.54−1.462010−1.02−0.912011−0.76−0.442012−0.38−0.132013−0.11−0.0420140.070.1920150.260.2720160.630.5320171.251.0120181.591.02Figure 3
Regression analysis diagram of the comprehensive scores of Jing-Jin-Ji Airport Group and the region.Figure 4
Regression analysis graph of the comprehensive scores of the Beijing-Tianjin-Hebei region and the airport group.Regression analysis of the comprehensive scores of Jing-Jin-Ji Airport Group and region.(1)
The regression equation fitted in isy = 0.7887x + 0.0048, and the degree of fit R2 = 0.959.(2)
The regression equation fitted in isy = 1.2025x + 0.0676, and the degree of fit R2 = 0.959.Calculate the mutual coordination degree between airport group subsystemi and regional subsystem j according to formulas (7)–(9), as shown in Table 7.Table 7
The calculation process of the coordination degree between the airport group subsystemi and the area subsystem j.
Yeari state coordination value required for jj state coordination value required for iU(i/j)U(j/i)C (i, j)2009−1.2097−1.82331.08541.0660.98212010−0.7997−1.16191.06691.05080.98492011−0.5946−0.59671.02761.02470.99722012−0.2949−0.261.01481.01880.99612013−0.0820−0.11561.00001.00180.998220140.06000.16091.00851.01740.991320150.20990.25721.00001.00360.996420160.50170.56971.00371.00080.997120170.99061.14691.01111.02000.991220181.25881.15901.08551.07460.9899According to the division of the degree of mutual coordination and adaptability of the adaptability evaluation, from 2009 to 2018, the degree of coordination between Jing-Jin-Ji Airport Group and the regional urban agglomeration was higher than 95%, basically in a highly coordinated state. This shows that the ten-year development has been basically stable. Both subsystems can meet each other’s development needs and can adapt to each other’s development system.It can be seen from Figure5 of the adaptability trend that the degree of mutual coordination between the airport group and the region has increased substantially since 2009, and the subsequent value has not been lower than that of 2009. This is related to the “Olympic effect” left over after the 2008 Olympics. After the 2008 Olympic Games, Beijing’s economic development has been relatively slow, and the extensive preparations for the early Olympic Games are time-consuming and expensive. After 2008, large-scale fund maintenance was carried out on the Olympic venues, resulting in a low-level period of urban construction, slow urban infrastructure construction, and slow overall urban economic development. However, due to the improvement of urban tourism efficiency after 2008, the Olympic Games have led to the rapid development of international tourism. Beijing’s tourism resources are becoming more abundant, and the civil aviation transportation industry is developing rapidly. However, the development of urban agglomerations and airport group at this stage has low adaptability and coordination.Figure 5
Airport group and regional adaptability trend map.From the perspective of the comprehensive score of the subsystem, with 0 as the dividing line, 0 indicates that the development of the system is at an average level. From the calculation of statistical data, there is no comprehensive score for both subsystems in a year, which also shows that airport group subsystem and regional subsystem will not reach the same level at the same time. It can be seen intuitively that the positive and negative boundaries of the airport group and the city group are from 2013 to 2014, and the comprehensive scores of the two subsystems have been increasing year by year, indicating that the development level and mutual coordination of the two are constantly improving.Since 2009, Jing-Jin-Ji Airport Group has been in a highly coordinated state with the region, which is mainly determined by the development trend of the Jing-Jin-Ji regional economy and airport group. Since 2009, the economic indicators of the Jing-Jin-Ji region have shown an upward trend. At the same time, the various indicators of the airport group in the Jing-Jin-Ji region have also shown a significant growth trend. The analysis results show that the growth of airport group indexes and regional indexes is basically synchronized. The airport group and the region are in a highly coordinated state. The development of the airport group in the Jing-Jin-Ji region can meet the needs of regional economic development, and the regional economic development also provides the necessary resources for Jing-Jin-Ji Airport Group. However, it does not indicate that Jing-Jin-Ji Airport Group and the region are in a high-level coordination state, and further analysis is needed.


### 3.2. Comparison Results of Airport Group Synergy

#### 3.2.1. Determining the Index Weight

(1) First-Level Indicator Weight. This study judged the importance of the first-level indicators of the airport group (Table 3) based on expert scores. The calculation results are shown in Table 8.Table 8
Judgment matrix.
XY1Y2Y3Y4wiwjAwjY115321.86710.46674.3675Y21/511/31/30.30580.07654.2105Y31/33131.10190.27554.3719Y41/231/310.72520.18134.0595First, normalize each column vector of matrix A, then sum by rows to getwi, then normalize wi to get wj, which is the approximate characteristic root, and finally calculate λ=1/n∑i=1nAwi/wi. as the approximate value of the largest characteristic root. Here, λmax=1/4×4.3675+4.2105+4.3719+4.0595=4.2524.Calculate the consistency index CI =CI=λmax−n/n−1=4.2524−4/4−1 0.0841 and obtain the 4th-order average random consistency index RI = 0.89 by looking up the table. The consistency ratio CR = CR=CI/RI=0.0945<0.1 the consistency of the matrix is acceptable, and wi is the first-level indicator weight of the system.(2) The Weight of Secondary Indicators. According to formulas (14)–(16) of the entropy method, the secondary index weights are calculated, as shown in Table 9.Table 9
Weights of secondary indicators.
Secondary indicatorsejdjwjDaily average flight density (freight)0.62020.37980.2962Domestic and international navigation points (number)0.62920.37080.2892International passenger transfer rate (%)0.46840.53160.4146Total annual passenger throughput (10,000 passengers)0.61930.38070.3772Total annual cargo and mail throughput (10,000 tons)0.68950.31050.3076Annual total number of takeoffs and landings (ten thousand)0.68170.31830.3152The diversity of airport public transportation options (types)0.89810.10190.9865Distance from airport to city (km)0.99860.00140.0135Average delay time (min)0.99920.00080.8889Airport departure flight punctuality rate (%)0.99990.00010.1111The comprehensive weight of the indicators is obtained from the first-level indicators and the second-level indicators, as shown in Table10.Table 10
Index weights of synergy.
First-level indicatorSecondary indicatorsWeightsComprehensive weightRoute network index (weight: 0.5042)Daily average flight density (freight)0.29620.1493Domestic and international navigation points (number)0.28920.1458International passenger transfer rate (%)0.41460.2097Air transport scale index (weight: 0.1475)Total annual passenger throughput (10,000 passengers)0.37720.0555Total annual cargo and mail throughput (10,000 tons)0.30760.0454Annual total number of takeoffs and landings (ten thousand)0.31520.0464Traffic convenience indexThe diversity of airport public transportation options (types)0.98650.1616(Weight: 0.1639)Distance from airport to city (km)0.01350.0021Airport service-level indexAverage delay time (min)0.88890.1638(Weight: 0.1844)Airport departure flight punctuality rate (%)0.11110.0204


#### 3.2.2. Evaluation Results of Synergy between Jing-Jin-Ji Airport Group and New York Airport Group

According to the weight of each index and formulas (11)–(13), the coordination index of Jing-Jin-Ji Airport Group and New York Airport Group can be calculated, as shown in Table 11.Table 11
Calculation results of the synergy index between Jing-Jin-Ji Airport Group and New York Airport Group.
Beijing-Tianjin-HebeiNew YorkSC0.74160.9624T0.39040.6084SD0.53810.7507As shown in Tables11 and 12, it can be seen that Jing-Jin-Ji Airport Group is in a barely synergetic stage, while New York Airport Group is in a good synergetic development stage. Therefore, the coordinated development of Jing-Jin-Ji Airport Group is far from the world-class airport group like New York Airport Group. It can be seen from formula (10) that the closer the development levels of the four aspects (route network, air transport scale, traffic convenience, and airport service level) are, the higher the coupling degree (SC) will be. Due to the wide gap between the four development indicators of Jing-Jin-Ji Airport Group, the overall coordination degree of Jing-Jin-Ji Airport Group is lower than that of New York Airport Group. The comprehensive coefficient index T value is directly proportional to the development of the four indicators. Therefore, the comprehensive evaluation index of Jing-Jin-Ji Airport Group is lower than that of New York Airport Group, which ultimately leads to a lower SD value of Jing-Jin-Ji Airport Group than New York Airport Group.Table 12
Synergy level.
Coordination degree SD≤0.490.5∼0.590.6∼0.690.7∼0.79≥0.8RankNot synergeticBarely synergeticMedium synergeticGood synergeticHigh-quality synergeticAccording to the characteristics of information entropy in the entropy method, the greater the degree of dispersion of the index, the greater the influence of the index on the comprehensive evaluation and the greater the weight. Therefore, the greater the weight of the synergy index, the more discrete the index, and the more obvious the difference between Jing-Jin-Ji Airport Group and New York Airport Group; from Table10, we can see that for the airline network index system, the biggest difference between the two airport groups is the international passenger transfer rate. The international passenger transfer rate of New York Airport Group is about four times that of Jing-Jin-Ji Airport Group. The throughput is less than twice, which is definitely not in line with the positioning of Jing-Jin-Ji Airport Group. And this indicator happens to represent the level of airport comprehensive management coordination. This shows that compared with New York Airport Group, Jing-Jin-Ji Airport Group needs to be improved on the road to internationalization. The international influence of New York Airport Group is higher than that of Jing-Jin-Ji Airport Group. As an international hub, it carries more international flights. Jing-Jin-Ji Airport Group can improve the passengers’ experience by improving the airport facilities, such as optimizing the flight time, forming a certain flight wave, and improving the layout of airport facilities. Let more passengers recognize Jing-Jin-Ji Airport Group as international transit and make it have a broader international influence.For the scale of air transportation, the annual passenger throughput is the most significant difference between Jing-Jin-Ji Airport Group and New York Airport Group. But overall, the annual passenger throughput of New York Airport Group is only 1.38 times that of Jing-Jin-Ji, and there is no big gap between the two. This shows that Jing-Jin-Ji Airport Group is developing rapidly and is also moving toward a world-class airport group. Moreover, the annual cargo and mail throughput of Jing-Jin-Ji Airport Group is higher than that of New York Airport Group. As a major import and export country, the airport group also plays a pivotal role in the world’s cargo hub. Compared with these more international airport groups, Jing-Jin-Ji Airport Group also has its own advantages.For the traffic convenience system, the major difference is the choice of airport public transportation. Analyze the factor of the distance between each airport in the two-airport group and the urban area. The airport is far from the city center, and there are few traffic routes to the city center or the railway station. It is inconvenient for residents to travel, and many passengers will not choose to travel by plane. Therefore, by improving the traffic route planning in the urban area, opening up the convenient route between the airport and the urban area, and perfecting the planned traffic route, the passenger flow on the land side can be quickly relieved and the development of aviation industry can be promoted.Finally, the airport service index has the greatest impact on the delay rate, which should be a common problem faced by the whole aviation industry, and aviation delay is inevitable. There are many reasons for the delay, and some are even uncontrollable. What we can do is to optimize the controllable factors to achieve the minimum delay rate.


#### 3.2.3. Cause Analysis

Compared with New York Airport Group, the level of coordination of Jing-Jin-Ji Airport Group is still relatively low, mainly due to the following reasons:(1)
Strong regional economic foundation. New York Airport Group is located in the busiest air transportation belt in the USA and is also the core area of the US economy. Its geographic location contributes approximately US$1.5 trillion to the USA every year. The powerful Northeast Air Corridor also benefits from the strong economic foundation of the northeast region. Less than 2% of the area provides the USA with 20% of the US GDP. Moreover, the current New York Airport Group is also the core area of the Northeast Aviation Corridor.(2)
Powerful integrated transportation network. New York Airport Group is mainly composed of Kennedy International Airport, Newark International Airport, and LaGuardia International Airport, among which the main civil aviation airports and business airports are within 30 kilometers of the urban area. New York Airport Group now adopts a regional transportation network that builds a multi-level interlocking sea, land, and air integration. Together with the subsequent cost of 3.8 billion US dollars, it has continuously strengthened the connection between the airport and the airport, and the airport and the city. Land has improved the airport’s transportation capacity. In 2003, the JFK International Airport rapid transit system was opened to directly connect airports, parking lots, railways, and subways to form a systematic regional transportation network, integrating aviation, railways, highways, and subways.(3)
Two large international aviation hubs. JFK Airport and Newark Airport have now become the two main aviation hubs of New York Airport Group. The two airports complement and compete with each other, forming the distinctive features of New York Airport Group. In 2018, the passenger throughput of JFK Airport was approximately 60 million, of which international passengers accounted for 59.3%. Newark has a throughput of around 50 million, with international passengers accounting for 37.2%. The two jointly assume the strong aviation network system of New York Airport Group and also assume the important international airport hub.(4)
Developed airport economic system. The rapid development of New York Airport Group makes the service industry around JFK Airport take a large proportion, attracting more international passengers. At the same time, numerous aerospace industries focus on regional supporting functions and continue to promote the integrated development of regional airport group.From the perspective of the internal environment of the airport, Jing-Jin-Ji Airport Group has a loose internal management structure compared with New York Airport Group. The resources of the airport group are unevenly distributed. The hub construction level of Jing-Jin-Ji Airport Group cannot meet the development of regional urban agglomerations, and a good balance has not been reached between the airport agglomeration and the urban agglomeration. The second is that the construction of the airport group’s airway system is not perfect. The airport economy still needs vigorous development, and the airport’s airport development hardware needs to be improved. This is also one of the factors that restrict the coordinated development of airport group and regions. Internal factors such as airspace resource constraints and flight schedule delays have largely restricted coordinated development. From an external point of view, the aviation service commercial facilities surrounding the airport group are not perfect. Strengthening the commercialization of the surrounding areas and the economic development of the catering and tourism industry will further promote the good synergetic development of the airport group and the city cluster. The surrounding transportation facilities and the integrated transportation elements connecting the airport group and the city group also directly affect the coordinated development of the two.


### 3.3. Suggested Measures for the Coordinated Development of Jing-Jin-Ji Airport Group and the Region

In summary, through the research on the adaptation coordination degree model and the coordination degree model (sections 3.4 and 3.5), it can be seen from Table3 that Jing-Jin-Ji Airport Group is currently in a low-level coordination and coordination stage, and the coordination of Jing-Jin-Ji Airport Group needs to be improved in the future. The level of coordination will gradually develop Jing-Jin-Ji Airport Group into a high-level coordinated and synergetic airport group.In order to better promote the coordinated development of Jing-Jin-Ji Airport Group and the region, it is necessary to clarify the cooperation of some workers in the airport group on the basis of national strategic planning and local government support, integrate resources, and strengthen the corresponding planning of the surrounding enterprises of the airport group. Reasonably allocate the resources of the region to the airport group, and play the leading role of the region. Furthermore, it effectively improves the utilization of airspace resources, strengthens the division of labor and cooperation among airport groups, effectively connects the transportation network between regional city cluster and airport group, strengthens the construction of airport economic systems, and promotes coordinated development of airport group and regions.


#### 3.3.1. Optimize Airspace Control and Deploy Flight Resource Allocation

Airspace constraints have always been an important factor affecting the development of the aviation industry, and the optimization of flight schedules has also been a topic that scholars have been working hard to solve in recent years. With the completion and commissioning of PKX Airport in 2019, the issue of airspace usage will become more prominent. Only by coordinating with the government’s policy guidance, rationally using the airspace and optimizing the flight schedules of the airport group, can we make better use of the airspace and promote aviation The development of the industry, in turn, plays a certain leading role in the development of the region.


#### 3.3.2. Speed Up the Airport Economy and Drive Regional Economic Development

Accelerate the development of airport economy, build a world-class airport economic zone, and effectively drive the growth of the airport group with the planning of coordinated industries. Relying on the hub airport, taking advantage of convenient transportation, gathering people, logistics, capital, and resources, developing modern service industries such as foreign trade, tourism, business conventions, and exhibitions, rationally arranging upstream and downstream industries in the aviation economy industrial chain, and developing aviation manufacturing (aircraft, parts, components, etc.), aviation maintenance, aviation logistics, general aviation (operations, training, entertainment, FBO), and other potential industries, promote the formation and development of the regional airport economic industry chain, promote the industrial upgrading and structural optimization of urban agglomerations, and promote related industries in urban agglomerations The division of labor and cooperation in China will improve the driving force of airport economy to regional development [25].


#### 3.3.3. Optimize the Structural System and Resource Integration of the Airport Group

It is necessary to formulate the development direction of the airport and adjust the system structure according to the overall development plan of the region. Strengthen the international hub functions of PEK Airport and PKX Airport, allocate more domestic small and medium-sized cities and short-haul international flights to TSN Airport and SJW Airport, and free up more international flights for PEK and PKX Airport. Build its own airport brand to alleviate the unbalanced development of Jing-Jin-Ji Airport Group. In particular, PKX Airport needs to open more international routes to enhance its role as an international hub, thereby enhancing the international influence of urban areas and promoting regional economic development. At the same time, the allocation of resources within the airport group must be uniformly configured so that airports at all levels can make reasonable use of resources. Strengthen close exchanges and cooperation between hub airports and small and medium airports. Guide the daily internal work exchanges among the members of the airport group, so that the exemplary leading role of the core airport can be brought into full play. Efforts should be made to seek development opportunities that are suitable for the region, identify their own positioning for each airport, make full use of resources to give full play to their advantages, professional division of labor, and collaborative cooperation, improve the overall service level of the airport group to the region, and promote coordinated development with the region.


#### 3.3.4. Optimize the Connection between the Airport Group and the Regional Integrated Transportation Network

The regional transportation network is closely related to the airport group. To expand the service scope of the airport group to the region, it is necessary to effectively implement air-rail combined transportation. In recent years, the city’s high-speed rail is developing rapidly. The city’s high-speed rail construction should be planned around the core hub airport and between the hub airport and the surrounding airports to make transportation between airports and between cities and airports more convenient. Strengthen the further connection between the airport group and the region, give play to the advantages of various modes of transportation, start with software and hardware, effectively connect the airport group with regional cities, improve the transfer efficiency of passengers, and guide the region by improving the efficiency and development of the airport. The overall development of air and rail transport will promote the integration of regional transportation.


#### 3.3.5. Give Full Play to the Leading Role of the Government

To strengthen the government’s decision-making and leading role in the civil aviation industry, on the one hand, it is to solve the problems of civil aviation and military aviation resource allocation and airspace occupation through government means, and to effectively promote the development of airports through government measures. Under the encouragement of the government, we will vigorously develop the aviation industry that is in line with the regional construction goals, rationally use resources, and further build the development of the airport group. On the other hand, the government is speeding up the improvement of the comprehensive transportation system of the airport group and improving the overall comprehensive transportation service level. The development of the airport industry is inseparable from government support. Local governments should strengthen the investment and construction of civil aviation, focus on improving the airport group’s airport economic industry, and build an integrated economic industrial chain for the regional airport group. In all aspects of the aviation industry development, protection and preferential policies are carried out to improve the coordinated development capabilities of the two.


## 3.1. Evaluation Results of Jing-Jin-Ji Airport Group and Regional Adaptability

In this study, SPSS (Statistical Product and Service Solutions) software was used for factor analysis. SPSS is a series of software products launched by IBM for statistical analysis, data mining, predictive analysis, and decision support. The comprehensive scores of the index factors of Jing-Jin-Ji Airport Group and the region were obtained. The data were standardized according to formula (1), and each index factor was calculated according to formulas (4)-(5). The comprehensive scores are shown in Table 6 and Figures 3 and 4.Table 6
Comprehensive scores of Jing-Jin-Ji Airport Group subsystem and regional subsystem.
YearComprehensive score of airport group subsystem iComprehensive score of regional subsystem j2009−1.54−1.462010−1.02−0.912011−0.76−0.442012−0.38−0.132013−0.11−0.0420140.070.1920150.260.2720160.630.5320171.251.0120181.591.02Figure 3
Regression analysis diagram of the comprehensive scores of Jing-Jin-Ji Airport Group and the region.Figure 4
Regression analysis graph of the comprehensive scores of the Beijing-Tianjin-Hebei region and the airport group.Regression analysis of the comprehensive scores of Jing-Jin-Ji Airport Group and region.(1)
The regression equation fitted in isy = 0.7887x + 0.0048, and the degree of fit R2 = 0.959.(2)
The regression equation fitted in isy = 1.2025x + 0.0676, and the degree of fit R2 = 0.959.Calculate the mutual coordination degree between airport group subsystemi and regional subsystem j according to formulas (7)–(9), as shown in Table 7.Table 7
The calculation process of the coordination degree between the airport group subsystemi and the area subsystem j.
Yeari state coordination value required for jj state coordination value required for iU(i/j)U(j/i)C (i, j)2009−1.2097−1.82331.08541.0660.98212010−0.7997−1.16191.06691.05080.98492011−0.5946−0.59671.02761.02470.99722012−0.2949−0.261.01481.01880.99612013−0.0820−0.11561.00001.00180.998220140.06000.16091.00851.01740.991320150.20990.25721.00001.00360.996420160.50170.56971.00371.00080.997120170.99061.14691.01111.02000.991220181.25881.15901.08551.07460.9899According to the division of the degree of mutual coordination and adaptability of the adaptability evaluation, from 2009 to 2018, the degree of coordination between Jing-Jin-Ji Airport Group and the regional urban agglomeration was higher than 95%, basically in a highly coordinated state. This shows that the ten-year development has been basically stable. Both subsystems can meet each other’s development needs and can adapt to each other’s development system.It can be seen from Figure5 of the adaptability trend that the degree of mutual coordination between the airport group and the region has increased substantially since 2009, and the subsequent value has not been lower than that of 2009. This is related to the “Olympic effect” left over after the 2008 Olympics. After the 2008 Olympic Games, Beijing’s economic development has been relatively slow, and the extensive preparations for the early Olympic Games are time-consuming and expensive. After 2008, large-scale fund maintenance was carried out on the Olympic venues, resulting in a low-level period of urban construction, slow urban infrastructure construction, and slow overall urban economic development. However, due to the improvement of urban tourism efficiency after 2008, the Olympic Games have led to the rapid development of international tourism. Beijing’s tourism resources are becoming more abundant, and the civil aviation transportation industry is developing rapidly. However, the development of urban agglomerations and airport group at this stage has low adaptability and coordination.Figure 5
Airport group and regional adaptability trend map.From the perspective of the comprehensive score of the subsystem, with 0 as the dividing line, 0 indicates that the development of the system is at an average level. From the calculation of statistical data, there is no comprehensive score for both subsystems in a year, which also shows that airport group subsystem and regional subsystem will not reach the same level at the same time. It can be seen intuitively that the positive and negative boundaries of the airport group and the city group are from 2013 to 2014, and the comprehensive scores of the two subsystems have been increasing year by year, indicating that the development level and mutual coordination of the two are constantly improving.Since 2009, Jing-Jin-Ji Airport Group has been in a highly coordinated state with the region, which is mainly determined by the development trend of the Jing-Jin-Ji regional economy and airport group. Since 2009, the economic indicators of the Jing-Jin-Ji region have shown an upward trend. At the same time, the various indicators of the airport group in the Jing-Jin-Ji region have also shown a significant growth trend. The analysis results show that the growth of airport group indexes and regional indexes is basically synchronized. The airport group and the region are in a highly coordinated state. The development of the airport group in the Jing-Jin-Ji region can meet the needs of regional economic development, and the regional economic development also provides the necessary resources for Jing-Jin-Ji Airport Group. However, it does not indicate that Jing-Jin-Ji Airport Group and the region are in a high-level coordination state, and further analysis is needed.


## 3.2. Comparison Results of Airport Group Synergy

### 3.2.1. Determining the Index Weight

(1) First-Level Indicator Weight. This study judged the importance of the first-level indicators of the airport group (Table 3) based on expert scores. The calculation results are shown in Table 8.Table 8
Judgment matrix.
XY1Y2Y3Y4wiwjAwjY115321.86710.46674.3675Y21/511/31/30.30580.07654.2105Y31/33131.10190.27554.3719Y41/231/310.72520.18134.0595First, normalize each column vector of matrix A, then sum by rows to getwi, then normalize wi to get wj, which is the approximate characteristic root, and finally calculate λ=1/n∑i=1nAwi/wi. as the approximate value of the largest characteristic root. Here, λmax=1/4×4.3675+4.2105+4.3719+4.0595=4.2524.Calculate the consistency index CI =CI=λmax−n/n−1=4.2524−4/4−1 0.0841 and obtain the 4th-order average random consistency index RI = 0.89 by looking up the table. The consistency ratio CR = CR=CI/RI=0.0945<0.1 the consistency of the matrix is acceptable, and wi is the first-level indicator weight of the system.(2) The Weight of Secondary Indicators. According to formulas (14)–(16) of the entropy method, the secondary index weights are calculated, as shown in Table 9.Table 9
Weights of secondary indicators.
Secondary indicatorsejdjwjDaily average flight density (freight)0.62020.37980.2962Domestic and international navigation points (number)0.62920.37080.2892International passenger transfer rate (%)0.46840.53160.4146Total annual passenger throughput (10,000 passengers)0.61930.38070.3772Total annual cargo and mail throughput (10,000 tons)0.68950.31050.3076Annual total number of takeoffs and landings (ten thousand)0.68170.31830.3152The diversity of airport public transportation options (types)0.89810.10190.9865Distance from airport to city (km)0.99860.00140.0135Average delay time (min)0.99920.00080.8889Airport departure flight punctuality rate (%)0.99990.00010.1111The comprehensive weight of the indicators is obtained from the first-level indicators and the second-level indicators, as shown in Table10.Table 10
Index weights of synergy.
First-level indicatorSecondary indicatorsWeightsComprehensive weightRoute network index (weight: 0.5042)Daily average flight density (freight)0.29620.1493Domestic and international navigation points (number)0.28920.1458International passenger transfer rate (%)0.41460.2097Air transport scale index (weight: 0.1475)Total annual passenger throughput (10,000 passengers)0.37720.0555Total annual cargo and mail throughput (10,000 tons)0.30760.0454Annual total number of takeoffs and landings (ten thousand)0.31520.0464Traffic convenience indexThe diversity of airport public transportation options (types)0.98650.1616(Weight: 0.1639)Distance from airport to city (km)0.01350.0021Airport service-level indexAverage delay time (min)0.88890.1638(Weight: 0.1844)Airport departure flight punctuality rate (%)0.11110.0204


### 3.2.2. Evaluation Results of Synergy between Jing-Jin-Ji Airport Group and New York Airport Group

According to the weight of each index and formulas (11)–(13), the coordination index of Jing-Jin-Ji Airport Group and New York Airport Group can be calculated, as shown in Table 11.Table 11
Calculation results of the synergy index between Jing-Jin-Ji Airport Group and New York Airport Group.
Beijing-Tianjin-HebeiNew YorkSC0.74160.9624T0.39040.6084SD0.53810.7507As shown in Tables11 and 12, it can be seen that Jing-Jin-Ji Airport Group is in a barely synergetic stage, while New York Airport Group is in a good synergetic development stage. Therefore, the coordinated development of Jing-Jin-Ji Airport Group is far from the world-class airport group like New York Airport Group. It can be seen from formula (10) that the closer the development levels of the four aspects (route network, air transport scale, traffic convenience, and airport service level) are, the higher the coupling degree (SC) will be. Due to the wide gap between the four development indicators of Jing-Jin-Ji Airport Group, the overall coordination degree of Jing-Jin-Ji Airport Group is lower than that of New York Airport Group. The comprehensive coefficient index T value is directly proportional to the development of the four indicators. Therefore, the comprehensive evaluation index of Jing-Jin-Ji Airport Group is lower than that of New York Airport Group, which ultimately leads to a lower SD value of Jing-Jin-Ji Airport Group than New York Airport Group.Table 12
Synergy level.
Coordination degree SD≤0.490.5∼0.590.6∼0.690.7∼0.79≥0.8RankNot synergeticBarely synergeticMedium synergeticGood synergeticHigh-quality synergeticAccording to the characteristics of information entropy in the entropy method, the greater the degree of dispersion of the index, the greater the influence of the index on the comprehensive evaluation and the greater the weight. Therefore, the greater the weight of the synergy index, the more discrete the index, and the more obvious the difference between Jing-Jin-Ji Airport Group and New York Airport Group; from Table10, we can see that for the airline network index system, the biggest difference between the two airport groups is the international passenger transfer rate. The international passenger transfer rate of New York Airport Group is about four times that of Jing-Jin-Ji Airport Group. The throughput is less than twice, which is definitely not in line with the positioning of Jing-Jin-Ji Airport Group. And this indicator happens to represent the level of airport comprehensive management coordination. This shows that compared with New York Airport Group, Jing-Jin-Ji Airport Group needs to be improved on the road to internationalization. The international influence of New York Airport Group is higher than that of Jing-Jin-Ji Airport Group. As an international hub, it carries more international flights. Jing-Jin-Ji Airport Group can improve the passengers’ experience by improving the airport facilities, such as optimizing the flight time, forming a certain flight wave, and improving the layout of airport facilities. Let more passengers recognize Jing-Jin-Ji Airport Group as international transit and make it have a broader international influence.For the scale of air transportation, the annual passenger throughput is the most significant difference between Jing-Jin-Ji Airport Group and New York Airport Group. But overall, the annual passenger throughput of New York Airport Group is only 1.38 times that of Jing-Jin-Ji, and there is no big gap between the two. This shows that Jing-Jin-Ji Airport Group is developing rapidly and is also moving toward a world-class airport group. Moreover, the annual cargo and mail throughput of Jing-Jin-Ji Airport Group is higher than that of New York Airport Group. As a major import and export country, the airport group also plays a pivotal role in the world’s cargo hub. Compared with these more international airport groups, Jing-Jin-Ji Airport Group also has its own advantages.For the traffic convenience system, the major difference is the choice of airport public transportation. Analyze the factor of the distance between each airport in the two-airport group and the urban area. The airport is far from the city center, and there are few traffic routes to the city center or the railway station. It is inconvenient for residents to travel, and many passengers will not choose to travel by plane. Therefore, by improving the traffic route planning in the urban area, opening up the convenient route between the airport and the urban area, and perfecting the planned traffic route, the passenger flow on the land side can be quickly relieved and the development of aviation industry can be promoted.Finally, the airport service index has the greatest impact on the delay rate, which should be a common problem faced by the whole aviation industry, and aviation delay is inevitable. There are many reasons for the delay, and some are even uncontrollable. What we can do is to optimize the controllable factors to achieve the minimum delay rate.


### 3.2.3. Cause Analysis

Compared with New York Airport Group, the level of coordination of Jing-Jin-Ji Airport Group is still relatively low, mainly due to the following reasons:(1)
Strong regional economic foundation. New York Airport Group is located in the busiest air transportation belt in the USA and is also the core area of the US economy. Its geographic location contributes approximately US$1.5 trillion to the USA every year. The powerful Northeast Air Corridor also benefits from the strong economic foundation of the northeast region. Less than 2% of the area provides the USA with 20% of the US GDP. Moreover, the current New York Airport Group is also the core area of the Northeast Aviation Corridor.(2)
Powerful integrated transportation network. New York Airport Group is mainly composed of Kennedy International Airport, Newark International Airport, and LaGuardia International Airport, among which the main civil aviation airports and business airports are within 30 kilometers of the urban area. New York Airport Group now adopts a regional transportation network that builds a multi-level interlocking sea, land, and air integration. Together with the subsequent cost of 3.8 billion US dollars, it has continuously strengthened the connection between the airport and the airport, and the airport and the city. Land has improved the airport’s transportation capacity. In 2003, the JFK International Airport rapid transit system was opened to directly connect airports, parking lots, railways, and subways to form a systematic regional transportation network, integrating aviation, railways, highways, and subways.(3)
Two large international aviation hubs. JFK Airport and Newark Airport have now become the two main aviation hubs of New York Airport Group. The two airports complement and compete with each other, forming the distinctive features of New York Airport Group. In 2018, the passenger throughput of JFK Airport was approximately 60 million, of which international passengers accounted for 59.3%. Newark has a throughput of around 50 million, with international passengers accounting for 37.2%. The two jointly assume the strong aviation network system of New York Airport Group and also assume the important international airport hub.(4)
Developed airport economic system. The rapid development of New York Airport Group makes the service industry around JFK Airport take a large proportion, attracting more international passengers. At the same time, numerous aerospace industries focus on regional supporting functions and continue to promote the integrated development of regional airport group.From the perspective of the internal environment of the airport, Jing-Jin-Ji Airport Group has a loose internal management structure compared with New York Airport Group. The resources of the airport group are unevenly distributed. The hub construction level of Jing-Jin-Ji Airport Group cannot meet the development of regional urban agglomerations, and a good balance has not been reached between the airport agglomeration and the urban agglomeration. The second is that the construction of the airport group’s airway system is not perfect. The airport economy still needs vigorous development, and the airport’s airport development hardware needs to be improved. This is also one of the factors that restrict the coordinated development of airport group and regions. Internal factors such as airspace resource constraints and flight schedule delays have largely restricted coordinated development. From an external point of view, the aviation service commercial facilities surrounding the airport group are not perfect. Strengthening the commercialization of the surrounding areas and the economic development of the catering and tourism industry will further promote the good synergetic development of the airport group and the city cluster. The surrounding transportation facilities and the integrated transportation elements connecting the airport group and the city group also directly affect the coordinated development of the two.


## 3.2.1. Determining the Index Weight

(1) First-Level Indicator Weight. This study judged the importance of the first-level indicators of the airport group (Table 3) based on expert scores. The calculation results are shown in Table 8.Table 8
Judgment matrix.
XY1Y2Y3Y4wiwjAwjY115321.86710.46674.3675Y21/511/31/30.30580.07654.2105Y31/33131.10190.27554.3719Y41/231/310.72520.18134.0595First, normalize each column vector of matrix A, then sum by rows to getwi, then normalize wi to get wj, which is the approximate characteristic root, and finally calculate λ=1/n∑i=1nAwi/wi. as the approximate value of the largest characteristic root. Here, λmax=1/4×4.3675+4.2105+4.3719+4.0595=4.2524.Calculate the consistency index CI =CI=λmax−n/n−1=4.2524−4/4−1 0.0841 and obtain the 4th-order average random consistency index RI = 0.89 by looking up the table. The consistency ratio CR = CR=CI/RI=0.0945<0.1 the consistency of the matrix is acceptable, and wi is the first-level indicator weight of the system.(2) The Weight of Secondary Indicators. According to formulas (14)–(16) of the entropy method, the secondary index weights are calculated, as shown in Table 9.Table 9
Weights of secondary indicators.
Secondary indicatorsejdjwjDaily average flight density (freight)0.62020.37980.2962Domestic and international navigation points (number)0.62920.37080.2892International passenger transfer rate (%)0.46840.53160.4146Total annual passenger throughput (10,000 passengers)0.61930.38070.3772Total annual cargo and mail throughput (10,000 tons)0.68950.31050.3076Annual total number of takeoffs and landings (ten thousand)0.68170.31830.3152The diversity of airport public transportation options (types)0.89810.10190.9865Distance from airport to city (km)0.99860.00140.0135Average delay time (min)0.99920.00080.8889Airport departure flight punctuality rate (%)0.99990.00010.1111The comprehensive weight of the indicators is obtained from the first-level indicators and the second-level indicators, as shown in Table10.Table 10
Index weights of synergy.
First-level indicatorSecondary indicatorsWeightsComprehensive weightRoute network index (weight: 0.5042)Daily average flight density (freight)0.29620.1493Domestic and international navigation points (number)0.28920.1458International passenger transfer rate (%)0.41460.2097Air transport scale index (weight: 0.1475)Total annual passenger throughput (10,000 passengers)0.37720.0555Total annual cargo and mail throughput (10,000 tons)0.30760.0454Annual total number of takeoffs and landings (ten thousand)0.31520.0464Traffic convenience indexThe diversity of airport public transportation options (types)0.98650.1616(Weight: 0.1639)Distance from airport to city (km)0.01350.0021Airport service-level indexAverage delay time (min)0.88890.1638(Weight: 0.1844)Airport departure flight punctuality rate (%)0.11110.0204


## 3.2.2. Evaluation Results of Synergy between Jing-Jin-Ji Airport Group and New York Airport Group

According to the weight of each index and formulas (11)–(13), the coordination index of Jing-Jin-Ji Airport Group and New York Airport Group can be calculated, as shown in Table 11.Table 11
Calculation results of the synergy index between Jing-Jin-Ji Airport Group and New York Airport Group.
Beijing-Tianjin-HebeiNew YorkSC0.74160.9624T0.39040.6084SD0.53810.7507As shown in Tables11 and 12, it can be seen that Jing-Jin-Ji Airport Group is in a barely synergetic stage, while New York Airport Group is in a good synergetic development stage. Therefore, the coordinated development of Jing-Jin-Ji Airport Group is far from the world-class airport group like New York Airport Group. It can be seen from formula (10) that the closer the development levels of the four aspects (route network, air transport scale, traffic convenience, and airport service level) are, the higher the coupling degree (SC) will be. Due to the wide gap between the four development indicators of Jing-Jin-Ji Airport Group, the overall coordination degree of Jing-Jin-Ji Airport Group is lower than that of New York Airport Group. The comprehensive coefficient index T value is directly proportional to the development of the four indicators. Therefore, the comprehensive evaluation index of Jing-Jin-Ji Airport Group is lower than that of New York Airport Group, which ultimately leads to a lower SD value of Jing-Jin-Ji Airport Group than New York Airport Group.Table 12
Synergy level.
Coordination degree SD≤0.490.5∼0.590.6∼0.690.7∼0.79≥0.8RankNot synergeticBarely synergeticMedium synergeticGood synergeticHigh-quality synergeticAccording to the characteristics of information entropy in the entropy method, the greater the degree of dispersion of the index, the greater the influence of the index on the comprehensive evaluation and the greater the weight. Therefore, the greater the weight of the synergy index, the more discrete the index, and the more obvious the difference between Jing-Jin-Ji Airport Group and New York Airport Group; from Table10, we can see that for the airline network index system, the biggest difference between the two airport groups is the international passenger transfer rate. The international passenger transfer rate of New York Airport Group is about four times that of Jing-Jin-Ji Airport Group. The throughput is less than twice, which is definitely not in line with the positioning of Jing-Jin-Ji Airport Group. And this indicator happens to represent the level of airport comprehensive management coordination. This shows that compared with New York Airport Group, Jing-Jin-Ji Airport Group needs to be improved on the road to internationalization. The international influence of New York Airport Group is higher than that of Jing-Jin-Ji Airport Group. As an international hub, it carries more international flights. Jing-Jin-Ji Airport Group can improve the passengers’ experience by improving the airport facilities, such as optimizing the flight time, forming a certain flight wave, and improving the layout of airport facilities. Let more passengers recognize Jing-Jin-Ji Airport Group as international transit and make it have a broader international influence.For the scale of air transportation, the annual passenger throughput is the most significant difference between Jing-Jin-Ji Airport Group and New York Airport Group. But overall, the annual passenger throughput of New York Airport Group is only 1.38 times that of Jing-Jin-Ji, and there is no big gap between the two. This shows that Jing-Jin-Ji Airport Group is developing rapidly and is also moving toward a world-class airport group. Moreover, the annual cargo and mail throughput of Jing-Jin-Ji Airport Group is higher than that of New York Airport Group. As a major import and export country, the airport group also plays a pivotal role in the world’s cargo hub. Compared with these more international airport groups, Jing-Jin-Ji Airport Group also has its own advantages.For the traffic convenience system, the major difference is the choice of airport public transportation. Analyze the factor of the distance between each airport in the two-airport group and the urban area. The airport is far from the city center, and there are few traffic routes to the city center or the railway station. It is inconvenient for residents to travel, and many passengers will not choose to travel by plane. Therefore, by improving the traffic route planning in the urban area, opening up the convenient route between the airport and the urban area, and perfecting the planned traffic route, the passenger flow on the land side can be quickly relieved and the development of aviation industry can be promoted.Finally, the airport service index has the greatest impact on the delay rate, which should be a common problem faced by the whole aviation industry, and aviation delay is inevitable. There are many reasons for the delay, and some are even uncontrollable. What we can do is to optimize the controllable factors to achieve the minimum delay rate.


## 3.2.3. Cause Analysis

Compared with New York Airport Group, the level of coordination of Jing-Jin-Ji Airport Group is still relatively low, mainly due to the following reasons:(1)
Strong regional economic foundation. New York Airport Group is located in the busiest air transportation belt in the USA and is also the core area of the US economy. Its geographic location contributes approximately US$1.5 trillion to the USA every year. The powerful Northeast Air Corridor also benefits from the strong economic foundation of the northeast region. Less than 2% of the area provides the USA with 20% of the US GDP. Moreover, the current New York Airport Group is also the core area of the Northeast Aviation Corridor.(2)
Powerful integrated transportation network. New York Airport Group is mainly composed of Kennedy International Airport, Newark International Airport, and LaGuardia International Airport, among which the main civil aviation airports and business airports are within 30 kilometers of the urban area. New York Airport Group now adopts a regional transportation network that builds a multi-level interlocking sea, land, and air integration. Together with the subsequent cost of 3.8 billion US dollars, it has continuously strengthened the connection between the airport and the airport, and the airport and the city. Land has improved the airport’s transportation capacity. In 2003, the JFK International Airport rapid transit system was opened to directly connect airports, parking lots, railways, and subways to form a systematic regional transportation network, integrating aviation, railways, highways, and subways.(3)
Two large international aviation hubs. JFK Airport and Newark Airport have now become the two main aviation hubs of New York Airport Group. The two airports complement and compete with each other, forming the distinctive features of New York Airport Group. In 2018, the passenger throughput of JFK Airport was approximately 60 million, of which international passengers accounted for 59.3%. Newark has a throughput of around 50 million, with international passengers accounting for 37.2%. The two jointly assume the strong aviation network system of New York Airport Group and also assume the important international airport hub.(4)
Developed airport economic system. The rapid development of New York Airport Group makes the service industry around JFK Airport take a large proportion, attracting more international passengers. At the same time, numerous aerospace industries focus on regional supporting functions and continue to promote the integrated development of regional airport group.From the perspective of the internal environment of the airport, Jing-Jin-Ji Airport Group has a loose internal management structure compared with New York Airport Group. The resources of the airport group are unevenly distributed. The hub construction level of Jing-Jin-Ji Airport Group cannot meet the development of regional urban agglomerations, and a good balance has not been reached between the airport agglomeration and the urban agglomeration. The second is that the construction of the airport group’s airway system is not perfect. The airport economy still needs vigorous development, and the airport’s airport development hardware needs to be improved. This is also one of the factors that restrict the coordinated development of airport group and regions. Internal factors such as airspace resource constraints and flight schedule delays have largely restricted coordinated development. From an external point of view, the aviation service commercial facilities surrounding the airport group are not perfect. Strengthening the commercialization of the surrounding areas and the economic development of the catering and tourism industry will further promote the good synergetic development of the airport group and the city cluster. The surrounding transportation facilities and the integrated transportation elements connecting the airport group and the city group also directly affect the coordinated development of the two.


## 3.3. Suggested Measures for the Coordinated Development of Jing-Jin-Ji Airport Group and the Region

In summary, through the research on the adaptation coordination degree model and the coordination degree model (sections 3.4 and 3.5), it can be seen from Table3 that Jing-Jin-Ji Airport Group is currently in a low-level coordination and coordination stage, and the coordination of Jing-Jin-Ji Airport Group needs to be improved in the future. The level of coordination will gradually develop Jing-Jin-Ji Airport Group into a high-level coordinated and synergetic airport group.In order to better promote the coordinated development of Jing-Jin-Ji Airport Group and the region, it is necessary to clarify the cooperation of some workers in the airport group on the basis of national strategic planning and local government support, integrate resources, and strengthen the corresponding planning of the surrounding enterprises of the airport group. Reasonably allocate the resources of the region to the airport group, and play the leading role of the region. Furthermore, it effectively improves the utilization of airspace resources, strengthens the division of labor and cooperation among airport groups, effectively connects the transportation network between regional city cluster and airport group, strengthens the construction of airport economic systems, and promotes coordinated development of airport group and regions.


### 3.3.1. Optimize Airspace Control and Deploy Flight Resource Allocation

Airspace constraints have always been an important factor affecting the development of the aviation industry, and the optimization of flight schedules has also been a topic that scholars have been working hard to solve in recent years. With the completion and commissioning of PKX Airport in 2019, the issue of airspace usage will become more prominent. Only by coordinating with the government’s policy guidance, rationally using the airspace and optimizing the flight schedules of the airport group, can we make better use of the airspace and promote aviation The development of the industry, in turn, plays a certain leading role in the development of the region.


### 3.3.2. Speed Up the Airport Economy and Drive Regional Economic Development

Accelerate the development of airport economy, build a world-class airport economic zone, and effectively drive the growth of the airport group with the planning of coordinated industries. Relying on the hub airport, taking advantage of convenient transportation, gathering people, logistics, capital, and resources, developing modern service industries such as foreign trade, tourism, business conventions, and exhibitions, rationally arranging upstream and downstream industries in the aviation economy industrial chain, and developing aviation manufacturing (aircraft, parts, components, etc.), aviation maintenance, aviation logistics, general aviation (operations, training, entertainment, FBO), and other potential industries, promote the formation and development of the regional airport economic industry chain, promote the industrial upgrading and structural optimization of urban agglomerations, and promote related industries in urban agglomerations The division of labor and cooperation in China will improve the driving force of airport economy to regional development [25].


### 3.3.3. Optimize the Structural System and Resource Integration of the Airport Group

It is necessary to formulate the development direction of the airport and adjust the system structure according to the overall development plan of the region. Strengthen the international hub functions of PEK Airport and PKX Airport, allocate more domestic small and medium-sized cities and short-haul international flights to TSN Airport and SJW Airport, and free up more international flights for PEK and PKX Airport. Build its own airport brand to alleviate the unbalanced development of Jing-Jin-Ji Airport Group. In particular, PKX Airport needs to open more international routes to enhance its role as an international hub, thereby enhancing the international influence of urban areas and promoting regional economic development. At the same time, the allocation of resources within the airport group must be uniformly configured so that airports at all levels can make reasonable use of resources. Strengthen close exchanges and cooperation between hub airports and small and medium airports. Guide the daily internal work exchanges among the members of the airport group, so that the exemplary leading role of the core airport can be brought into full play. Efforts should be made to seek development opportunities that are suitable for the region, identify their own positioning for each airport, make full use of resources to give full play to their advantages, professional division of labor, and collaborative cooperation, improve the overall service level of the airport group to the region, and promote coordinated development with the region.


### 3.3.4. Optimize the Connection between the Airport Group and the Regional Integrated Transportation Network

The regional transportation network is closely related to the airport group. To expand the service scope of the airport group to the region, it is necessary to effectively implement air-rail combined transportation. In recent years, the city’s high-speed rail is developing rapidly. The city’s high-speed rail construction should be planned around the core hub airport and between the hub airport and the surrounding airports to make transportation between airports and between cities and airports more convenient. Strengthen the further connection between the airport group and the region, give play to the advantages of various modes of transportation, start with software and hardware, effectively connect the airport group with regional cities, improve the transfer efficiency of passengers, and guide the region by improving the efficiency and development of the airport. The overall development of air and rail transport will promote the integration of regional transportation.


### 3.3.5. Give Full Play to the Leading Role of the Government

To strengthen the government’s decision-making and leading role in the civil aviation industry, on the one hand, it is to solve the problems of civil aviation and military aviation resource allocation and airspace occupation through government means, and to effectively promote the development of airports through government measures. Under the encouragement of the government, we will vigorously develop the aviation industry that is in line with the regional construction goals, rationally use resources, and further build the development of the airport group. On the other hand, the government is speeding up the improvement of the comprehensive transportation system of the airport group and improving the overall comprehensive transportation service level. The development of the airport industry is inseparable from government support. Local governments should strengthen the investment and construction of civil aviation, focus on improving the airport group’s airport economic industry, and build an integrated economic industrial chain for the regional airport group. In all aspects of the aviation industry development, protection and preferential policies are carried out to improve the coordinated development capabilities of the two.


## 3.3.1. Optimize Airspace Control and Deploy Flight Resource Allocation

Airspace constraints have always been an important factor affecting the development of the aviation industry, and the optimization of flight schedules has also been a topic that scholars have been working hard to solve in recent years. With the completion and commissioning of PKX Airport in 2019, the issue of airspace usage will become more prominent. Only by coordinating with the government’s policy guidance, rationally using the airspace and optimizing the flight schedules of the airport group, can we make better use of the airspace and promote aviation The development of the industry, in turn, plays a certain leading role in the development of the region.


## 3.3.2. Speed Up the Airport Economy and Drive Regional Economic Development

Accelerate the development of airport economy, build a world-class airport economic zone, and effectively drive the growth of the airport group with the planning of coordinated industries. Relying on the hub airport, taking advantage of convenient transportation, gathering people, logistics, capital, and resources, developing modern service industries such as foreign trade, tourism, business conventions, and exhibitions, rationally arranging upstream and downstream industries in the aviation economy industrial chain, and developing aviation manufacturing (aircraft, parts, components, etc.), aviation maintenance, aviation logistics, general aviation (operations, training, entertainment, FBO), and other potential industries, promote the formation and development of the regional airport economic industry chain, promote the industrial upgrading and structural optimization of urban agglomerations, and promote related industries in urban agglomerations The division of labor and cooperation in China will improve the driving force of airport economy to regional development [25].


## 3.3.3. Optimize the Structural System and Resource Integration of the Airport Group

It is necessary to formulate the development direction of the airport and adjust the system structure according to the overall development plan of the region. Strengthen the international hub functions of PEK Airport and PKX Airport, allocate more domestic small and medium-sized cities and short-haul international flights to TSN Airport and SJW Airport, and free up more international flights for PEK and PKX Airport. Build its own airport brand to alleviate the unbalanced development of Jing-Jin-Ji Airport Group. In particular, PKX Airport needs to open more international routes to enhance its role as an international hub, thereby enhancing the international influence of urban areas and promoting regional economic development. At the same time, the allocation of resources within the airport group must be uniformly configured so that airports at all levels can make reasonable use of resources. Strengthen close exchanges and cooperation between hub airports and small and medium airports. Guide the daily internal work exchanges among the members of the airport group, so that the exemplary leading role of the core airport can be brought into full play. Efforts should be made to seek development opportunities that are suitable for the region, identify their own positioning for each airport, make full use of resources to give full play to their advantages, professional division of labor, and collaborative cooperation, improve the overall service level of the airport group to the region, and promote coordinated development with the region.


## 3.3.4. Optimize the Connection between the Airport Group and the Regional Integrated Transportation Network

The regional transportation network is closely related to the airport group. To expand the service scope of the airport group to the region, it is necessary to effectively implement air-rail combined transportation. In recent years, the city’s high-speed rail is developing rapidly. The city’s high-speed rail construction should be planned around the core hub airport and between the hub airport and the surrounding airports to make transportation between airports and between cities and airports more convenient. Strengthen the further connection between the airport group and the region, give play to the advantages of various modes of transportation, start with software and hardware, effectively connect the airport group with regional cities, improve the transfer efficiency of passengers, and guide the region by improving the efficiency and development of the airport. The overall development of air and rail transport will promote the integration of regional transportation.


## 3.3.5. Give Full Play to the Leading Role of the Government

To strengthen the government’s decision-making and leading role in the civil aviation industry, on the one hand, it is to solve the problems of civil aviation and military aviation resource allocation and airspace occupation through government means, and to effectively promote the development of airports through government measures. Under the encouragement of the government, we will vigorously develop the aviation industry that is in line with the regional construction goals, rationally use resources, and further build the development of the airport group. On the other hand, the government is speeding up the improvement of the comprehensive transportation system of the airport group and improving the overall comprehensive transportation service level. The development of the airport industry is inseparable from government support. Local governments should strengthen the investment and construction of civil aviation, focus on improving the airport group’s airport economic industry, and build an integrated economic industrial chain for the regional airport group. In all aspects of the aviation industry development, protection and preferential policies are carried out to improve the coordinated development capabilities of the two.


## 4. Conclusion

Jing-Jin-Ji Airport Group plays an important role in the development of the entire region and even the country. On the basis of consulting relevant literature, this study analyzes the connotation of the coordinated development of airport groups and regions, explores the internal and external causes and their interaction mechanism, and studies the coordinated relationship between airport groups and regions by using adaptability evaluation model and collaborative evaluation model. Finally, it puts forward some measures remedial for the coordinated development of Jing-Jin-Ji Airport Group and region. The main research conclusions are as follows:(1)
By selecting the representative index system, the adaptability evaluation model of airport group and regional development is established, and the adaptability level of Jing-Jin-Ji Airport Group and regional development is obtained. Since 2009, the coordination degree between Jing-Jin-Ji Airport Group and regional development has been greater than 0.9, which shows that the development in the past ten years has been basically stable. The two subsystems can meet each other’s development needs and can adapt to each other’s development system.(2)
Since 2014, the comprehensive scores of the two subsystems of Jing-Jin-Ji Airport Group and the region have been increasing year by year, indicating that the development level and mutual coordination of the two are constantly improving. However, it does not mean that Jing-Jin-Ji Airport Group and the region are in a high-level coordination state, and the degree of coordination is also evaluated.(3)
In order to more intuitively study the coordination level of Jing-Jin-Ji Airport Group, this study selects New York Airport Group as a reference. Through the study of the synergy evaluation model, it is found that the degree of coordination of Jing-Jin-Ji Airport Group is significantly lower than compared with it. New York Airport Group is in barely coordination.(4)
In order to improve the level of coordinated development between Jing-Jin-Ji Airport Group and the region, it is necessary to optimize the airspace, allocate flight resources, accelerate the development of airport economy, optimize the airport group structure system and resource integration, and give play to the leading role of the government. Continue to work hard to speed up Jing-Jin-Ji Airport Group to reach the stage of high-quality coordination.The coordinated development index of airports and regions is affected by many aspects. In this paper, some typical indicators are selected to study the cooperative development relationship between the two, and there are some difficulties in data collection, which need to be improved. In the future, we can consider adding more indicators for research and analysis, adding multiple indicators under the jurisdiction of regional economy, transportation, environment, etc., and selecting more detailed data to conduct a deeper research on the mechanism of coordinated development between airport clusters and regions.



---

*Source: 3974316-2022-07-09.xml*