the same as an airway. The part of the earth’s surface over which the air line passes is called its route. Air lines of the USSR flown by civil aviation airplanes are classified as union, local, or international. Union air lines are interconnected and connect Moscow and several other cities of the country with republic, krai, and oblast centers, indus-trial regions, and the country’s major health resorts. Local air lines connect raions, through which settlements and large sovkhozes and kolkhozes are connected to the centers of oblasts, krais, and republics. International air lines extend beyond the national boundaries of the USSR and connect it with other countries.