As evidence that the interrelation between airlinks and urban hierarchy reinforces the hegemony of big cities over time, a new study by IBGE shows that São Paulo is the most central spot of the air network in the Brazilian territory, accordingly to its demography, its economic role and its position among global cities.  Being the only "great national metropolis", with the biggest population and the highest GDP in the country, the city was the leader in the ranking, with a flow of 26,848,944 passengers and 201,132,886 kg of cargo in 2010. Rio de Janeiro, on the other hand, has lost some of its relative importance in air traffic network, although it still holds a second position in passenger transportation (14,467,527 passengers, in 2010), with a less significant position in cargo transportation (37,296,620 kg, the fifth among the 19 cities in the ranking of major cargo handling).

These and other data can be found in the publication "Airlinks 2010", which places Brazilian cities in the national urban system from the perspective of air transportation, by describing and analyzing passenger and cargo flows, and also the accessibility of cities, provinding  information on cost and journey time between them.

The work makes use of a double database: pairs of "origin-destination" links in regular air transportation between Brazilian cities (based on information by ANAC - National Agency of Civil Aviation) and data on costs and journey time from the Global Distribution System (GDS).

The study shows that, according to ANAC, 135 (2.4%) out of the 5,565 existing municipalities in 2010 had an airport with regular flights.  The pairs of links analyzed amounted to 877, with a total 71,750,986 passengers and 434 thousand metric tons of cargo transported.  

An air link is a link between two cities, operated by a commercial airline, not including connecting flights, and counted at every disembark.

The compete study is available at

ftp://geoftp.ibge.gov.br/redes_e_fluxos_do_territorio/ligacoes_aereas/

The survey calls attention to the highly polarized structure of air traffic flow. In 2010, almost 50% of the total connections in the country were concentrated in only 25 pairs of cities. The link between São Paulo and the other six biggest metropolises in the country (Rio de Janeiro, Brasília, Porto Alegre, Salvador, Belo Horizonte and Curitiba) represented more than 25% of the total passengers transported, and, among the main one connected São Paulo and Rio: 5,680,873 passengers.  

Air transportation of cargo is even more concentrated, due to its high costs, with more than half of the traffic concentrated in only 10 pairs of links. The link between São Paulo and Manaus itself encompassed, alone, more than 20% of the total cargo transported in 2010.

Cost, journey time and physical distance

The survey emphasizes how much accessibility through aviation depends on the the urban hierarchy, classifying cities in terms of accessibility regarding  journey time and price. It stresses that the distance barrier does not cause the main effects, ant that the economic ties of the territory, as well as historical interactions can overcome distance when it comes to accessibility.

It also highlights how changes in journey time and costs are influenced by regional differences, so that, in general, the more distant from the core area of the country (hegemonic are from the economic point-of-view) a city or region is, the worse the accessibility to it by air. Therefore, although the North Region is the least accessible one, both in terms of cost and of journey time, in the Central-South some areas such as the inner part of Rio Grande do Sul, for example, are also little privileged. The high centralization of the urban network in the capital of that state is reflected on the higher costs and longer trips to smaller cities.

In general terms, however, the standards of internal inequality are common in Brazilian domestic flights: the Central-South region remains relatively privileged in terms of territory accessibility, the Northeast presents a good status in the capitals and the North Region is the most remote and least accessible of the Major Regions.  

The mere fact of having an airport with regular flights somehow reflects how central a city can be. This way, each one of the 135 airports in the 5,565 Brazilian municipalities (ANAC, 2010) has a considerable area of influence, attracting users from their surroundings.

São Paulo is the main polarizing center of passenger transportation, leading practically all the cities which have an airport, either directly or indirectly.

In secondary air traffic flows of passengers (the second biggest one of city "A" to city "B") it is possible to realize that São Paulo now shares a number of links with other centers, being important to highlight the notable increase of Rio de Janeiro’s importance. The role of Belém also calls attention, since now it holds the traffic that comes from the mining activity in cities of southeastern Paraná. Brasília still holds some relative importance, being the secondary destination of São Paulo and other cities from the North, Central West and Northeast Regions.

Brasília, Salvador and Campinas: peculiar situations

This work highlights peculiar situations, such as the cases of Brasília, Salvador and Campinas. The first one benefits from its central position in the territory, which facilitates connectivity with the network, mainly considering the North and part of the Northeast Region. Besides being a major traffic rotator at national level, the capital of the country performs a significant role in the generation of this same traffic, since it houses fundamental elements for the functioning of the Nation.

The number of passengers of Salvador is in accordance with its position in urban hierarchy and with its role as a widely known tourist route. The capital of Bahia is also used as a hub (an airport which functions as a spot for the redistribution of passengers and/or cargo among the destinations covered by a given airline). 

Campinas, in the state of São Paulo, despite its evolution as a major intermediate stop in cargo transportation, does not appear equivalent highlight in the study, because the matrix of the air lnk analyzed is not limited to national air traffic and the airport of Viracopos is mainly characterized by the flow of international cargo.

In 2010, the international airport of Campinas had a flow of 255,951,023 kg of international cargo, amounting to 97% of the total cargo transported in the airport. Only the remaining 3% belonged to domestic traffic. The cargo segment, however, is less influenced by urban hierarchy than the passenger segment, due, partly, to features of the aviation sector: the high cost of transportation per unit makes only long-distance calls economically viable, whereas shorter distances are usually covered by other means of transportation.

Structural changes in the country and the loss of influence by Rio

In the historical evolution of links, it is possible to observe a general scenario of stability, with concentration of air traffic flows in the South, and the progressive increases of volumes towards the South and the northeastern capitals.

Important changes can be observed, nevertheless.  First, in the starting years surveyed there is a disproportionate concentration of the flow of passengers in the Rio-São Paulo air shuttle, whereas connections with other cities are fairly limited. This situation changes in the beginning of the 1980's and is reinforced in the 1990's with the progressive increase of access to this type of transportation. There has also been a progressive change of the main shuttle, from Rio de Janeiro to São Paulo.  

It is important to notice that, until 1985, the metropolis of Rio de Janeiro formed the major hub of national aviation, and polarized a big part of traffic. This tendency is more commonly observed in cargo transportation, where the economic hegemony of São Paulo is seen more promptly. In the 1980’s it was also possible to observe, mainly in cargo connections, one of the structural changes of the Brazilian urban network: the strengthening of flows from the North Region with direct departures from Manaus and Porto Velho to the Central-South region, flying around the connection through Belém.

This situation of Rio de Janeiro results from structural changes of the Brazilian economy in the last few decades, with decentralization of the industrial and productive activity and of the concentration of management and control activities in São Paulo, and includes the restructuring of airlines.  Besides bankruptcies, acquisition and merging in the market, airlines that operate domestic flights took a big part of their operationg staffs to São Paulo, causing  relative emptying of airports in Rio de Janeiro – although between 2005 and 2010 there was bigger increase of the number of passengers in Rio de Janeiro (50.6%), when compared to São Paulo (23.5%).

The analysis of dominant air trafic flows (air connections of a higher value departing from a city) evidences that Rio de Janeiro has lost its relative importance in the network. According to previous studies, between 1965 and 1973, Rio featured as a major independent center (urban center whose dominant flow heads towards a smaller city), at national level, with São Paulo in a complementary relationship in passenger transportation. The chart of 2010, however, shows that the city fell from its position as an area of national reach, encompassing all the North and Northeast region, to that of an area reduced to limited to neighboring airports: those of Rio de Janeiro state itself, of the south of Minas Gerais, of São José dos Campos and of Campinas. The specific behavior of the latter is explained by the "traffic-shadow effect" of airports in São Paulo, which happens when the biggest city in a certain area works as a polarizing center of long-distance air transportation, reducing short-distance air traffic levels of the smaller surrounding cities.