An international airport is an airport with customs and border control facilities enabling passengers to travel between countries around the world. International airports are usually larger than domestic airports and most feature longer runways and facilities to accommodate the heavier aircraft such as the Boeing 747 commonly used for international and intercontinental travel. International airports often also host domestic flights, which often help feed both passengers and cargo into international ones (and vice versa).
Buildings, operations and management have become increasingly sophisticated since the mid-20th century, when international airports began to provide infrastructure for international civilian flights. Detailed technical standards have been developed to ensure safety and common coding systems implemented to provide global consistency. The physical structures that serve millions of individual passengers and flights are among the most complex and interconnected in the world. By the second decade of the 21st century, there were over 1,200 international airports and almost two billion international passengers along with 50 million metric tonnes of cargo passing through them annually.