Regardless of the net-work structure, trade imbalances often make it difficult for airlines to fill avail-able cargo space. For example, the demand for cargo capacity from China to the United States greatly exceeds the demand for capacity from the United States to China—and this trend is expected to accelerate over the next few years. Some flights will, as a result, travel relatively empty in one direction. Airlines need to obtain traffic rights (called "freedoms of the air") from foreign governments to operate internationally. There are a total of nine freedoms that describe the right of one nation's carrier to operate in another country. The first freedom, for example, is the right to fly across the territory of a foreign country without landing; the second freedom is the right to land in a foreign country to refuel or for other purposes. These freedoms are typically ex-changed between countries, and a carrier must apply for the traffic right referred to in these international agreements