Many early terminals were built in the 1930s–1940s when air travel become popular. They are often in the art deco style architecture of the time. One such example from 1940 is the Houston Municipal Airport Terminal. Early airport terminals opened directly onto the tarmac: passengers would walk or take a bus to their aircraft. This design is still common among smaller airports. Many larger airports have "bus gates" to access aircraft which are parked beyond the main terminal.