Many airlines operate outside their main hubs and bases as focus cities. For example, Qantas operates focus cities in Melbourne and Singapore aside from its main hub in Sydney. Another would be Ryanair's 40-plus bases scattered over Europe (above). The benefits of operating base cities can be enormous, in which I will explain below.

To create focus cities on Airline Mogul, your airline must operate at least four gates from another airport of your choice in the world, making sure that you operate it to at least 75% of capacity, or else the extra, unused gates will be removed after two days (equivalent to two months). There are two types of bases, in which it is the basis for what you see on all worlds on Airline Mogul:

• Domestic: your chosen base city is located within your home continent (for example, when you open a base in the United States, you can open bases within the country, as well as Alaska, Canada, and Hawaii). In Airline Mogul terms, it is counted as one (1) base.
• Foreign (International): your chosen base city is located outside your home continent (for example, if you have a base in France, and you open a base in Turkey, it is considered as foreign since Turkey is grouped with the Middle East). In Airline Mogul terms, it is counted as two (2) bases.

You might also want to look at where you can actually build your bases since different worlds have different operating locations:

It is best for your airline to look at these base creation restrictions so that your airline will stay in shape in terms of route development and rules compliance. If you are more of an adventurous type, go for worlds that are listed with the  ∞  (infinity) symbol, meaning you can create "unlimited" number of hubs. Be careful, however, on where the symbol is seen, as in the third picture, because some worlds permit unlimited number of bases, but give you a limit on foreign bases.

Let's say for example, your airline operates dozens, if not hundreds, of routes around your region or worldwide, and you have been renting over a dozen gates to keep your operations running (this could apply to your home airport or any of your focus cities). You then stumble upon this question: now that my airline is growing rapidly, is it time for me to build a terminal on my home airport (or any of my bases)?

My answer: it really depends on how much growth you project your airline to grow. For example, an airline called Glad Airways has been operating over 60 routes nonstop from its home airport in Frankfurt using various aircraft. And the airline is projected to operate to over 100 routes out of the Frankfurt metropolitan area. In the process, several airlines compete with Glad on certain routes, thus reducing the number of gates available for the airline to use. In that case, Glad could choose to build a terminal to keep up with his growth plans, as well as opening up more gates for other airlines to use.

Below is the basic premise of building a terminal:

• In order for you to build a terminal from your home airport, make sure that you need to have a certain amount of money in your bank to allow construction of a new terminal (usually running over  € 5,000,000). Start the process by highlighting the "Operations" tab on the menu then clicking on the "Build Terminal" tab.
• In order for your desired terminal to be built, make sure that your chosen airport has at least five (5) gates in operation before making one -- basically, if you have made focus cities (see left) with a minimum of five gates, those are qualified for terminal creation.
• You need to construct at least five gates, which would be separate from the cost of building a new terminal, so that you can operate it from your home airport.
• Once you have fulfilled the financial obligations needed to build a terminal, Airline Mogul will then automatically build a terminal for you, and you have the option to return your rented gates.

If you would like to convert some of your base (focus) cities into terminals, follow the same procedure as above. An added bonus: should you build your own terminal, and you start off building with 10 gates, Airline Mogul will automatically return one of your rented gates to the airport at no additional charge for your airline.

Once you have built a terminal, you won't see the "Gate Return Warning" message from Airline Mogul anymore since you have paid for operating the gates at your terminal. However, it becomes tricky when you start building more flights out of your terminal and suddenly end up running out of gates. In that case, instead of doing Gate Search, you will head back to "Build Terminal" under operations, then you will see "Extend Terminal". Find the airport you want to add gates in, and it will construct the gates once you have sufficient funds to do so.