O'Hare International Airport

Soon after the opening of Chicago Municipal Airport in 1926, the City of Chicago realized more airport capacity would be needed. The city government investigated various sites in the 1930s but made little progress before America's entry into World War II.^[10]

O'Hare began as a manufacturing plant for Douglas C-54 Skymasters during World War II. The site was known as Orchard Place, previously a small German-American farming community. The 2 million square feet (190,000 m²) plant, in the northeast corner of what is now the airport, needed easy access to the workforce of the nation's second-largest city, as well as its railroads and location far from enemy threat. 655 C-54s were built at the plant, more than half of all produced. The airfield, from which the C-54s flew out, was known as Douglas Airport; initially, it had four 5,500-foot (1,700 m) runways.^[10] Less known is the fact that it was the location of the Army Air Force's 803rd Specialized Depot,^[20] a unit charged with storing many captured enemy aircraft; a few representatives of this collection would eventually be transferred to the Smithsonian Institution's National Air and Space Museum.^[21][22]

Douglas Company's contract ended with the war's conclusion. Douglas considered building airliners at Orchard but chose to concentrate civil production at its headquarters in Santa Monica, California.^[10] With the departure of Douglas, the complex took the name Orchard Field Airport, and was assigned the IATA code ORD.^[23]

The United States Air Force used the field extensively during the Korean War; the airport then had no scheduled airline service. Although not its primary base in the area, the Air Force used O'Hare as a fighter base; it was home to the 62nd Fighter-Interceptor Squadron flying North American F-86 Sabres from 1950 to 1959.^[24] By 1960, the need for O'Hare as an active duty fighter base was diminishing, just as commercial business was picking up at the airport. The Air Force removed active-duty units from O'Hare and turned the station over to Continental Air Command, enabling them to base reserve and Air National Guard units there.^[25] As a result of a 1993 agreement between the City and the Department of Defense, the reserve base was closed on April 1, 1997, ending its career as the home of the 928th Airlift Wing and of the 126th Air Refueling Wing in 1999. At that time, the remaining 357-acre (144 ha) site came under the ownership of the Chicago Department of Aviation.^[26]

In 1945, Chicago mayor Edward Kelly established a board to choose the site of a new airport to meet future demand. After considering various proposals, the board decided upon the Orchard Field site and acquired most of the federal government property in March 1946. The military retained a small parcel of property on the site and the right to use 25% of the airfield's operating capacity for free.^[10]

Ralph H. Burke devised an airport master plan based on the pioneering idea of what he called "split finger terminals", allowing a terminal building to be attached to "airline wings" (concourses), each providing space for gates and planes. (Pre-war airport designs had favored ever-larger single terminals, exemplified by Berlin's Tempelhof.) Burke's design also included underground refueling, direct highway access to the front of terminals, and direct rail access from downtown, all of which are utilized at airports worldwide today.^[27] O'Hare was the site of the world's first jet bridge in 1958,^[28][29] and successfully adapted slip form paving, developed for the nation's new Interstate highway system, for seamless concrete runways.

In 1949, the City renamed the facility O'Hare Airport to honor Edward "Butch" O'Hare, the U.S. Navy's first flying ace and Medal of Honor recipient in World War II.^[30] Its IATA code (ORD) remained unchanged, however, resulting in O'Hare being one of the few IATA codes bearing no connection to the airport's name or metropolitan area.^[23]

Scheduled passenger service began in 1955,^[31] but growth was slow at first. Although Chicago had invested over $25 million in O'Hare, Midway remained the world's busiest airport and airlines were reluctant to move until highway access and other improvements were completed.^[32] The April 1957 Official Airline Guide listed 36 weekday departures from O'Hare, while Midway had 414. Improvements began to attract the airlines: O'Hare's first international terminal opened in August 1958, and by April 1959 the airport had expanded to 7,200 acres (2,900 ha) with new hangars, terminals, parking and other facilities. The expressway link to downtown Chicago, now known as the Kennedy Expressway, was completed in 1960.^[31] And new Terminals 2 and 3, designed by C. F. Murphy and Associates, opened on January 1, 1962.^[33]

The biggest factor driving airlines to relocate their operations from Midway to O'Hare was the jet airliner; the first scheduled jet at O'Hare was an American 707 from New York to Chicago to San Francisco on March 22, 1959.^[34] One-mile-square (2.6-kilometer-square) Midway had no space for the runways that 707s and DC-8s required. Airlines had been reluctant to move to O'Hare, but they naturally did not want to split their operations: in July 1962, the last fixed-wing scheduled airline flight in Chicago moved from Midway to O'Hare. Until United returned in July 1964, Midway's only scheduled airline was Chicago Helicopter Airways. The arrival of Midway's traffic quickly made O'Hare the world's busiest airport, serving 10 million passengers annually. Within two years, that number would double, with Chicagoans boasting that more people passed through O'Hare in 12 months than Ellis Island had processed in its entire existence. O'Hare remained the world's busiest airport until it was eclipsed by Hartsfield-Jackson Atlanta International Airport in 1998.

O'Hare had four runways in 1955;^[35] 8,000 foot (2,400 m) runway 14R/32L opened in 1956 and was extended to 11,600 feet (3,500 m) a few years later, allowing nonstops to Europe. Runway 9R/27L (now 10L/28R) opened in 1968 and runway 4R/22L in 1971.

In the 1980s, after passage of US airline deregulation, the first major change at O'Hare occurred when TWA left Chicago for St. Louis as its main mid-continent hub.^[36] Although TWA had a large hangar complex at O'Hare and had started Constellation nonstops to Paris in 1958, by the time of deregulation its operation was losing $25 million a year under competition from United and American.^[37] Northwest likewise ceded O'Hare to the competition and shifted to a Minneapolis/St. Paul and Detroit-centered network by the early 1990s after acquiring Republic Airlines in 1986.^[38] Delta maintained an O'Hare hub for some time, even commissioning a new Concourse L in 1983.^[39] Ultimately, Delta found competing from an inferior position at O'Hare too expensive and closed its Chicago hub in the 1990s, concentrating its upper Midwest operations at Cincinnati.

The dominant hubs established at O'Hare in the 1980s by United and American continue to operate today. United developed a new two-concourse Terminal 1 (dubbed "The Terminal for Tomorrow"), designed by Helmut Jahn. It was built between 1985 and 1987 on the site of the original Terminal 1; the structure, which includes 50 gates, is best known for its curved glass forms and the connecting underground tunnel between Concourses B and C.^[40] The tunnel is illuminated with a neon installation titled Sky's the Limit (1987) by Canadian artist Michael Hayden, which plays an airy, slow-tempo version of Rhapsody in Blue.^[41] American renovated and expanded its existing facilities in Terminal 3 from 1987 to 1990; those renovations feature a flag-lined entrance hall to Concourses H/K.^[42]

The demolition of the original Terminal 1 in 1984 to make way for Jahn's design forced a "temporary" relocation of international flights into facilities called "Terminal 4" on the ground floor of the airport's central parking garage. International passengers were then transferred by bus to and from their aircraft. Relocation finally ended with the completion of the 21-gate International Terminal in 1993 (now called Terminal 5); it contains all customs facilities. Its location, on the site of the original cargo area and east of the terminal core, necessitated the construction of a peoplemover, which connected the terminal core with the new terminal as well as remote rental and parking lots.^[39]

Following deregulation and the buildup of the American and United hubs, O'Hare faced increasing delays from the late 1980s onward due to its inefficient runway layout; the airfield had remained unchanged since the addition of its last new runway (4R/22L) in 1971.^[43] O'Hare's three pairs of angled runways were meant to allow takeoffs into the wind, but they came at a cost: the various intersecting runways were both dangerous and inefficient. Official reports at the end of the 1990s ranked O'Hare as one of the worst-performing airports in the United States based on the percentage of delayed flights.^[44] In 2001, the Chicago Department of Aviation committed to an O'Hare Modernization Plan (OMP). Initially estimated at $6.6 billion, the OMP was to be paid by bonds issued against the increase in the federal passenger facility charge enacted that year and federal airport improvement funds.^[45] The modernization plan was approved by the FAA in October 2005 and involved a complete reconfiguration of the airfield. The OMP included the construction of four new runways, lengthening two existing runways, and decommissioning three old runways to provide O'Hare with six parallel runways and two crosswind runways.^[46]

The OMP was the subject of legal battles, both with suburbs who feared the new layout's noise implications as well as with survivors of persons interred in a cemetery the city proposed to relocate; some of the cases were not resolved until 2011.^[47] These issues, plus the reduction in traffic as a result of the 2008 financial crisis, delayed the OMP's completion; construction of the sixth and final parallel runway (9C/27C) began in 2016.^[48] Its completion in 2020, along with an extension of runway 9R/27L completed in 2021, concluded the OMP.^[49]

In 2018, the city and airlines committed to Phase I of a new Terminal Area Plan dubbed O'Hare 21. The plan was to build two all-new satellite concourses to the southwest of Concourse C, and to expand Terminals 2 and 5 with additional gates, lounges, and updates to operations all over the airport. (Terminal 5 has ten new gates in addition to its newly expanded facilities, plus two additional gates to each accommodate an Airbus A380.)^[50] The expansion will enable same-terminal transfers between international and domestic flights, faster connections, improved facilities and technology for TSA and customs inspections and much larger landside amenities such as shopping and restaurants. A principal feature of the plan is the reorganization of the terminal core into an "alliance hub," the first in North America; airside connections and layout will be optimized around airline alliances. This will be made possible by the construction of the O'Hare Global Terminal (OGT) where Terminal 2 currently stands. The OGT and two new satellite concourses will allow for expansion for both American's and United's international operations as well as easy interchange with their respective Oneworld (American) and Star Alliance (United) partner carriers, eliminating the need to transfer to Terminal 5.

This project will add over 3 million square feet (280,000 m²) to the airport's terminals, add a new customs processing center in the OGT, reconstruct gates and concourses (new concourses will be a minimum of 150 feet (46 m) wide), increase the gate count from 185 to 235, and provide 25% more ramp space at every gate throughout the airport to accommodate larger aircraft.^[51] After an international design competition that featured public voting on five final architectural proposals, the Studio ORD group, led by architect Jeanne Gang (in collaboration with SCB, Corgan, Milhouse, and STL Architect), was selected to design the OGT,^[52][53] while Skidmore, Owings & Merrill LLP will design Satellites 1 and 2.^[54] By terms of the agreement, total costs of $8.5 billion for the project are to be borne by bonds issued by the city, which will be retired by airport usage fees paid by the airlines. O'Hare 21 is scheduled for completion of the two satellite terminals in 2028, and overall completion in 2030.^{[55][56][needs update]}

In November 2023, the project's cost had ballooned far over budget leading both American Airlines and United Airlines to call for the global terminal project to be cancelled or scaled back.^[57] Later in May 2024, American Airlines and United Airlines were able to reach an agreement with the City of Chicago to allow the project to continue. In the agreement, the replacement of Terminal 2 would be accelerated, while the addition of the two satellite concourse would be delayed. The replacement of Terminal 2 with the OGT was deemed more critical to complete first instead of the satellite concourses.^[58]

O'Hare has four numbered passenger terminals with nine lettered concourses and a total of 213 gates- the most of any airport in the world.^[59]

• Terminal 1 is used for United Airlines, Lufthansa and All Nippon Airways flights. It contains 52 gates on two concourses, lettered B–C.^[59]
• Terminal 2 is used for most United Express and some mainline United flights, as well as all Air Canada, Alaska Airlines, and JetBlue flights. It contains 41 gates on two concourses, lettered E–F.^[59]
• Terminal 3 is used for American Airlines, Aer Lingus, British Airways, Iberia, Japan Airlines, and Spirit Airlines flights. It contains 80 gates on four concourses, lettered G, H, K, and L.^[59]
• Terminal 5 is used for Delta Air Lines, Frontier Airlines and Southwest Airlines flights, as well as all international airlines save for those that depart from Terminals 1–3.^[60][61] Terminal 5 is also used for non-pre–cleared international arrivals, as it currently contains the airport's U.S. Customs and Border Protection facilities.^[62] It contains 35 non-sequential gates on a single concourse with the highest number being 40, lettered M. (Note that Terminal 5 is very long, so be prepared for a 20 minute walk.)

Terminals 1–3 are interconnected airside via a walkway.^[63] Terminal 5 is separated from the other terminals by a set of taxiways that cross over the airport's access road, requiring most passengers to exit security, ride a shuttle bus or take the Airport Transit System and then re–clear security. An additional shuttle bus provides an airside connection from Terminals 1 and 3 to Terminal 5, operating every 15 minutes from 11:30 am to 9:30 pm.^[63]

O'Hare has two sets of parallel runways, one on either side of the terminal complex. Each airfield has three parallel east–west runways (9L/27R, 9C/27C, and 9R/27L on the north side; 10L/28R, 10C/28C, and 10R/28L on the south side) and a crosswind runway oriented northeast–southwest (4L/22R on the north, 4R/22L on the south). The north crosswind runway, 4L/22R, sees limited usage due to intersecting 9R/27L and 9C/27C;^[64] however, runway 22L is often used for takeoffs during what is called "west flow" on the main runways. The airfield is managed by three FAA air traffic control towers. O'Hare has a voluntary nighttime (22:00–07:00) noise abatement program.^[65]

In 2015, runway 32R/14L was permanently closed after 72 years of service, in favor of the new runway 10R/28L.^[66]

Currently, O'Hare has the most runways of any civilian airport in the world, totaling eight.^{[citation needed]}

The Hilton Chicago O'Hare is between the terminal core and parking garage and is currently the only hotel on airport property. It is owned by the Chicago Department of Aviation and operated under an agreement with Hilton Hotels, who extended their agreement with the city by ten years in 2018.^[67]

The Airport Transit System shuttles passengers between the terminal core (Terminals 1–3), Terminal 5, and the O'Hare Multi-Modal Facility (MMF).^[68] The system, which re-opened on November 3, 2021, resumed round-the-clock service starting at 5 a.m. on Monday, April 18, 2022,^[69] after a nearly six-year renovation.^[70] Meanwhile, free shuttle buses also continue to run 24/7 and contribute to congestion, boarding on the upper (departures) level of all terminals. The Bus Shuttle center, located on the ground level of the parking garage between Terminals 1–3 and directly opposite the Hilton Hotel, provides a temporary boarding location for local hotel shuttles and regional public transport buses.^[71] The O'Hare Multi-Modal Facility is the home of all on-airport car rental firms as well as some extended parking.^[72] In addition, the Chicago-area commuter rail system, Metra, has a transfer station of its North Central Service (NCS) located at the northeast corner of the MMF; however, the NCS currently operates an occasional schedule on weekdays only.^[73]

The CTA Blue Line's north terminus is at O'Hare and provides direct service to downtown via the Milwaukee–Dearborn subway in the Loop and continuing to west suburban Forest Park. Trains depart at intervals ranging from every four to thirty minutes, 24 hours a day.^[74] The station is located on the lower level of the parking garage, and can be accessed directly from Terminals 1–3 via tunnel and from Terminal 5 via shuttle bus.

Pace, Peoria Charter, Van Galder Bus Company, and Wisconsin Coach Lines operate bus service to O'Hare, stopping at the MMF.

O'Hare is directly served by Interstate 190, which offers interchanges with Mannheim Road (U.S. 12 and 45), the Tri-State Tollway (Interstate 294), and Interstate 90. I-90 continues as the Kennedy Expressway into downtown Chicago and becomes the Jane Addams Memorial Tollway northwest to Rockford and the Wisconsin state line.

There are presently two main cargo areas at O'Hare. The South Cargo Area was relocated in the 1980s from the airport's first air cargo facilities, located east of the terminal core, where Terminal 5 now stands. Many of the structures in this new cargo area then had to be rebuilt, again, to allow for the OMP and specifically runway 10R/28L; as a result, what is now called the South Cargo Area is located between 10R/28L and 10C/28C. This large collection of facilities, in three sections (Southwest, South Central, and Southeast), was established mainly by traditional airline-based air cargo; Air France Cargo, American, JAL Cargo, KLM, Lufthansa Cargo, Northwest and United all built purpose-built, freestanding cargo facilities,^[75] although some of these are now leased out to dedicated cargo firms. In addition, the area contains two separate facilities for shipper FedEx and one for UPS.^[75]

The Northeast Cargo Area (NEC) is a conversion of the former military base (the Douglas plant area) at the northeast corner of the airport property. It is a new facility designed to increase O'Hare's cargo capacity by 50%. Two buildings currently make up the NEC: a 540,000 square feet (50,000 m²) building completed in 2016,^[76] and a 240,000 square feet (22,000 m²) building that was completed in 2017.^[77] A third structure will complete the NEC with another 150,000 square feet (14,000 m²) of warehouse space.^[78]

The current capability of the cargo areas provide 2 million square feet (190,000 m²) of airside cargo space with parking for 40 wide-body freighters matched with over 2 million square feet (190,000 m²) of landside warehousing capability. O'Hare shipped over 1,700,000 tonnes (1,900,000 short tons) in 2018, fifth among airports in the U.S.^[79]

In 2011, O'Hare became the first major airport to build an apiary on its property; every summer, it hosts as many as 75 hives and a million bees. The bees are maintained by 30 to 40 ex-offenders with little to no work experience and few marketable skills; they are primarily recruited from Chicago's North Lawndale neighborhood. They are taught beekeeping but also benefit from the bees' labor, turning it into bottled fresh honey, soaps, lip balms, candles and moisturizers marketed under the beelove product line.^[80][81] More than 500 persons have completed the program, transferring to jobs in manufacturing, food processing, customer service, and hospitality; the repeat-offender rate is reported to be less than 10%.^[82]

The CDA's Airport Airfield Operations section is based out of the 150 ft (50 m) tall prototype tower architect I.M. Pei designed for the FAA in the 1960s -1970s.

^1 : Ethiopian Airlines flight from Addis Ababa to O'Hare stops at Rome–Fiumicino,^[163] but the flight from O'Hare to Addis Ababa is non-stop.

The following is a list of major crashes or incidents that occurred to planes at O'Hare, on approach, or just after takeoff from the airport:^[193]

• On September 17, 1961, Northwest Orient Airlines Flight 706, a Lockheed L-188 Electra, crashed upon takeoff, killing all 37 on board.^[194]
• On August 16, 1965, United Airlines Flight 389, a Boeing 727, crashed 30 miles (48 km) east of O'Hare while on approach, killing all 30 on board.^[195]
• On December 27, 1968, North Central Airlines Flight 458, a Convair CV-580, crashed into a hangar at O'Hare, killing 27 on board and one on the ground.^[196]
• On December 20, 1972, North Central Airlines Flight 575, a Douglas DC-9, crashed upon takeoff after colliding with Delta Airlines Flight 954, a Convair CV-880 which was taxiing across the active runway; 10 passengers on the DC-9 were killed.^[197]
• On May 25, 1979, American Airlines Flight 191, a McDonnell Douglas DC-10 on a Memorial Day weekend flight to Los Angeles International Airport, had its left engine detach while taking off from runway 32R, then stalled and crashed into a field some 4,600 feet (1,400 m) away. 273 died, including two on the ground, in the deadliest single-aircraft crash in United States history, and the worst aviation disaster in U.S. history prior to the September 11, 2001 attacks.^[198][199]
• On March 19, 1982, a United States Air Force KC-135 Stratotanker crashed upon approach to O'Hare 40 miles (64 km) northwest of the city (near Woodstock), killing 27 people on board.^[200]
• On February 9, 1998, American Airlines Flight 1340, a Boeing 727, crashed upon landing from Kansas City, injuring 22 passengers.^[201]
• On October 28, 2016, American Airlines Flight 383 aborted takeoff on runway 28R after a fire broke out in the right engine of the Boeing 767-300ER; 20 passengers and one flight attendant were injured.^[202]
• On April 9, 2017, a passenger was forced off of a Republic-operated United Express flight in Chicago bound for Louisville. The passenger was escorted off the flight by Chicago Department of Aviation officers after he refused to give up his seat to an airline employee. He attempted to run back onto the aircraft but was removed. A video posted on social media showing him being injured and dragged off the plane led to a public outcry.

• List of the world's busiest airports, for a complete list of the busiest airports in the world
• List of airports in Illinois
• Chicago Union Station

•  This article incorporates public domain material from the Air Force Historical Research Agency