The city earlier signed a contract with Studio ORD, headed by Chicago designer Jeanne Gang, to build a new global terminal where the decades-old Terminal 2 now stands.

Combined with a related expansion of Terminal 5 that already is underway, the projects will add dozens of new gates to the congested airfield, expanding space by 60 percent. The city also is promising more modern facilities, and improved shopping and retail opportunities.

The third design group which was selected today, HNTB, will design less visible but still critical aspects of the expansion, including a central tunnel system that will move utilities, baggage and passengers among the terminals. Details of its contract have yet to be negotiated.

“Having two or three lead designers in place and working in parallel is a critical moment for the overall success of the O’Hare 21 program,” city Aviation Commissioner Jamie Rhee said in a statement. “We have assembled a team of unparalleled vision and talent, and every traveler who uses O’Hare will benefit.”

Skidmore's $140 million is nearly as much as the $160 million Gang's firm is getting for the flashier Global Terminal. Both are huge projects, officials said, with the satellite terminals alone roughly the size of all of Midway Airport’s passenger facilities.