Leasing gates

Having access to another airport in which to operate your routes requires you to lease a gate (or, when your finances are sufficiently strong later in the game and you must expand beyond the current allotment, you may build a terminal).

A lease represents a month-to-month commitment by your airline to utilize at least one slot available for the gate, and further obligates your airline to pay for the entirety of the gate regardless of your utilization.