Read the article "The History of O'Hare International Airport" and answer the question. Planning for the construction of O'Hare International Airport began in 1945 when a committee chose Orchard Field as the location of the future airport. In 1955, the airport opened to commercial air traffic and O'Hare International Airport served as a hub for travelers throughout the world.

To respond to the increasing number of passengers, the airport expanded. O'Hare added a fifth runway and opened a terminal for international travel. Passengers could take flights to other countries and throughout the United States. The amount of land used by the airport grew to about 7,200 acres. This expansion included airplane hangars, cargo buildings, and even a post office. Next, there was an expressway built to connect O'Hare International Airport with downtown Chicago. People could travel to and from the airport quickly and easily, making it a desirable location. Finally, the main terminal building and parking lot were completed. These expansions led to a greater number of passengers. In 1962, 10 million passengers traveled through the airport that year alone. O'Hare was officially the world's busiest airport.

O'Hare's growth was accompanied by innovation. In order to increase efficiency, the airport developed a task force that allowed three runways to be used at the same time in 1976. The Passenger Facility Charge, which charged passengers for using the airport, was introduced in 1990. This money was used to improve and modernize the airport. The Airport Transit System was created to help transport passengers between terminals in 1993.

In 1996, the O'Hare Noise Compatibility Commission was created to help surrounding neighborhoods deal with aircraft noise. To aid with the O'Hare Modernization Program, a Sustainable Design Manual was created in 2003. This cutting-edge document helped the airport think about the environment during the modernization process. The principles outlined in the manual were later used in a similar document in August 2009 that promoted environmental sustainability at the airport. Over the years, O'Hare International Airport has grown and innovated to manage its expansion.

What is the overall structure of this text?

Cause and effect
Chronological order
Compare and contrast
Problem and solution