“国内線” refers to domestic flights that operate within a single country. These flights connect various cities and regions, allowing passengers to travel quickly and efficiently without crossing international borders. Domestic airlines typically offer a range of services, including economy and business class options. In many countries, such as 日本 and アメリカ, domestic flights are a popular choice for both business and leisure travelers. They are often more affordable than international flights and can significantly reduce travel time compared to driving or taking a train. Domestic airports facilitate these flights, providing essential services for passengers.