Airportman.id – The traffic growth at an airport, in general, will increase from year to year in line with the economic development of the city or country. To anticipate this traffic growth, airport managers will expand or add airport facilities to maintain minimum service standards for airport users.

In general, those that will be increased in area or number include the addition of parking stands, the construction of rapid exit taxiways, the addition of departure gates, or the number of parking lots for public vehicles. The addition of this facility will continue to be carried out until the airport can no longer be developed due to limited land or other technical factors causing the airport to become overcapacity.

To solve this problem, it is necessary to build one or more new airports to support the operations of existing airports. The operation of two or more airports is known as a multi-airport system.

The main/existing airport is called the primary airport, and the second airport is called the secondary airport. In general, secondary airports have passenger traffic between 10-50% of the primary airport. These airports have relatively the same catchment area coverage. Generally, they occur in big cities and metropolitan areas as the main generator of the country's largest aircraft passenger traffic producer.

Major cities in the world with a multi-airport system include London, Paris, New York, San Francisco, Seoul, Berlin, and Tokyo. London has six airports, namely Heathrow, London City, Gatwick, Standsted, Southend, and Luton. Tokyo has two airports, namely Narita and Haneda. France has Charles De Gaulle and Orly Airports. One of the metropolitan areas with a multi-airport system in the San Francisco metro area includes the cities of San Francisco, Oakland, and San Jose, where each city has an airport.

The division of functions between the main airport and supporting airports is generally influenced by the type of airline and the destination/destination of the flight. Airlines with full-service services usually use the main airport as their base of operations, while the supporting airports become the basis for Low-Cost Carriers (LCC)/no-frills airlines. For example, London-Stansted Airport is the base for LCC Ryanair, and Full-service British Airways dominate Heathrow Airport.

The division of airport functions according to flight destinations, for example, is Haneda Airport and Kansai Airport. Haneda serves 90% of domestic destinations, and Kansai serves international destinations. The three airports in Moscow-Russia are divided by function according to flight destinations. Sheremetyevo Airport is focused on serving international flights. Domodedovo Airport serves flights to eastern Russia such as Siberia, the Urals, and other cities in Eastern Russia. Meanwhile, Vnukovo Airport serves flights to southern Russia or Ukraine.

The development of two or more airports in one city apart from technical reasons, such as overcapacity at an existing airport, can also be caused by other reasons such as political reasons, defense, and security, or considerations of a region's economic growth.

An example of a multi-airport airport built for political reasons is the airport in Berlin. In 1945 Germany was divided into two parts, namely West Germany and East Germany, as compensation for their defeat in the Second World War. Berlin is also divided into West Berlin, controlled by the allied countries (US, UK, France), and East Berlin, controlled by the Soviet Union. East Berlin airport is Berlin Schoenefeld Airport and West Berlin airport is Tegel Airport. After the collapse of the Soviet Union in 1991, many flights at Schoenefeld Airport were diverted to Tegel Airport. To support the operation of this airport, the German government developed a new airport by utilizing the Schoenefeld runway, namely Brandenburg Airport.

Airports with a multi-airport system built with a defense and security background include three airports in Moscow-Russia, namely Sheremetyevo, Domodedovo, and Vnukovo.

The development of an airport with a multi-airport system to reduce growing inequality between regions is the North Bali Airport development plan. The North Bali Airport development plan, which has been studied since 2012, aims to increase economic growth in the northern region of the island of Bali. As we know, the highest economic growth on the Island of the Gods is currently still centered in the south of Bali, such as Denpasar City and Badung Regency.

Planning for airport development with a multi-airport concept becomes more complicated than planning for a single airport system. Suppose it is a single airport that serves a city without having other competitors in the vicinity. In that case, the airport development plan will be based on a passenger traffic forecast study at that airport. Suppose there is no force majeure, such as a pandemic, war, et cetera.. In that case, the airport construction plan will estimate the construction time for the expansion of airport facilities and the size of the facilities.

Meanwhile, in planning for airports with a multi-airport system, it becomes more challenging to consider the forecast/growth of passenger traffic because there are other factors such as competing airports and more volatile market dynamics. Changes in an airline's policy to move its operating base from one airport to another in a multi-airport system, the existence of a bankrupt LCC airline, or the incentives given by an airport to passengers or airlines can cause changes in the number of passenger traffic at the airport. These changes make airport development planning more difficult because the uncertainty factor is higher than the single airport system.

To anticipate errors in the preparation of passenger traffic forecasts as a reference in airport development, Richard de Neufville, in his book Airport System Planning Design, recommends that airport managers continue to follow market dynamics developments related to the growth of airline traffic at surrounding airports.

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In addition, it is necessary to divide the stages of airport development more than usual. Airport development to the ultimate stage is generally divided into three to five stages.

Especially for airports with a multi-airport system, the stages can be expanded. This is necessary to anticipate if it turns out that after the construction, there is a change in the aviation market so that the use of these facilities is not optimal, then the risk of loss can be reduced. With more stages, there will be more development alternatives, if necessary, changes to the airport development design to keep up with market dynamics that can change in a short time. The layout of airport facilities is also designed to be as flexible as possible to accommodate changes in airport development design.