Chicago's O'Hare International Airport is expected to undergo a major overhaul as the city and airlines finalize an $8.5 billion expansion project.

Citing sources familiar with the negotiations, the Chicago Tribune reported the eight-year plan would be the largest in the airport's history, adding a new global terminal, dozens of additional gates and multiple concourses. Altogether, the renovation would add more than 3.1 million square feet of terminal space, that, combined with ongoing runway expansion, would allow the airport to increase capacity.

The proposed project calls for Terminal 2 to be replaced with a Global Terminal better suited to accommodate international flights and Terminals 1, 3 and 5 to be renovated. The Global Terminal would then be connected to two new satellite concourses via an underground pedestrian tunnel.

Other notable additions include a new western parking and security screening facility for airline employees, a parking garage at Terminal 5 and a trio of baggage systems.

While the airlines have agreed in principle to three hotel projects at the airport, those plans won't be finalized until later this year.

According to Aviation Commissioner Ginger Evans, the project would be funded by bonds backed by future higher airline fees. She also said passengers shouldn't anticipate an increase in airfares as airport costs only represent about 5 to 6 percent of carriers' total operating costs.

"The non-hub airlines get their own space in Terminal 5, their own entrance, their own hotel, more club room, more paid space, they will be closer to the city. They love that," an unidentified source told the Tribune. "And American and United essentially get a better internationally connecting complex, because to send passengers over to or from Terminal 5 is a pain in the ass. Nobody likes that. So, in the end, American, United and the other non-hub airlines all agreed. It gives everyone sort of what they want."

READ MORE: American Plans Major Expansion at Chicago O’Hare

If agreed to, passengers would also benefit from larger 150-foot-wide concourses and 50,000-square-foot American and United club lounges inside the new Global Terminal.

What's more, by having domestic and international airlines in the same terminal, O'Hare would rival London's Heathrow Airport and Tokyo's Narita International Airport as the first "global alliance hub" in the U.S., according to Evans.

It's predicted that the expansion would propel Chicago's total number of passengers from 78 million in 2016 to roughly 100 million by 2026.