Firms that didn't make the cut included BIG, HOK, Gensler and even Chicago architect Jahn, whose principal, Helmut Jahn, designed O'Hare terminal 1 which opened in 1986 when his firm was still known as Murphy/Jahn.

The overhaul, dubbed O’Hare 21, aims to nearly double the airport’s overall footprint from 5.5 million sq ft to 8.9 million sq ft. The plan includes a new customs processing center in a global terminal that will replace the existing United terminal 2, renovation of three other existing terminals, the addition of 25% more ramp space at existing gates to accommodate larger aircraft, an increase of the gate count to 235 from 185, and the addition of two new remote satellite concourses. A tunnel to a new parking facility and a western terminal are also part of the vision.

Former Chicago aviation commissioner Ginger Evans led the planning process from 2015 until her departure from the position in August, and negotiated the new use and lease agreement between Chicago and five O’Hare airlines—United, American, Spirit, Delta and Jet Blue—which allowed bonds to be sold to finance the expansion. The airlines have pledged to pay the entire construction cost back to the city through fees for the new gates as part of the deal. 

Evans says the idea of the global terminal is two-fold. “One is to place our international customers in the heart of O’Hare," which is where terminal 2 is today, so they can connect to domestic flights in terminal 1 with United and with American Airlines in terminal 3. "In addition to that physical connector, our vision is to have a technology connection so that we can incorporate the screening and pre-clearance of international passengers," she says,

The plan also will make O'Hare the first U.S. airport to use a baggage image and weight identification system, which is designed to streamline the customs process by capturing image and weight information for each bag brought onboard. This would allow U.S. Customs and Border Protection to positively match each bag and passenger at the new global terminal so that passengers can move from there to a domestic flight without further screening.

The shortlisted teams have been invited by Chicago to participate in a request for proposals for lead architectural design services. Through the RFP process, this winter, each team will submit a design model that will be showcased at various locations throughout Chicago. The City will seek public feedback on the design concepts presented by each of the five finalist teams. This input will be taken into consideration as part of the final selection.

“Chicago has called upon some of the world’s best designers to help carry out our vision for the new O’Hare global terminal—the key to a bigger, better and more modern O’Hare for the 21st century,” Mayor Emanuel said in a press release.

Transportation, business and civic leaders from Chicago will make up the official selection committee with additional technical advisory from leading architectural firms, cultural and academic institutions and local businesses.

"This procurement represents an opportunity for the Department [of Procurement Services] to play a role in a historic moment for the city. We are committed to ensuring the integrity of the procurement process and continuing our partnership with Aviation and all stakeholders as we move forward," said Shannon Andrews, commissioner of procurement services.

O'Hare's terminal 5 is scheduled to be the first terminal to be expanded, with construction starting in late 2019.