Competition to build an elusive high-speed rail line between downtown and a soon-to-be-expanded O’Hare Airport has been narrowed to two teams — and visionary billionaire Elon Musk is the captain of one of them.

Musk’s The Boring Company plans to create a “high-speed loop” using “electric pods” in underground tunnels he claims can be built for far less money because of the “boring” technology he has pioneered.

He will vie against O’Hare Xpress LLC, whose power player participants include Meridiam, Antarctica Capital, JLC Infrastructure, Mott MacDonald and First Transit.

Two other teams that responded to the city’s Round One “request for qualifications” (RFQ) were eliminated amid questions about their “ability to deliver the critical project with no public subsidy.”

A “request for proposals” (RFP) will be issued Friday — due back on May 18 — that will determine the winner.

It will permit travel corridors above or below ground and require stations at O’Hare and downtown with the possibility of finally using the empty Block 37 super-station that former Mayor Richard M. Daley spent $200 million to build.

“We set forth a pretty ambitious proposal for fast service from downtown to O’Hare at no public cost and two significant … companies and consortia have responded that they can do it,” Deputy Mayor Bob Rivkin said Tuesday.

“One is proposing a more traditional rapid rail service. The other is proposing a tunnel service. Cost components will be different. But the city won’t be on the hook for any of it.”

The area below Block 37 is back in the mix as a potential site for express train service to O’Hare. Mayor Rahm Emanuel is shown last year talking to reporters about the plans. | Rich Hein/Sun-Times

By moving to the RFP stage, City Hall is further along than it has ever been in delivering express service between downtown and O’Hare.

But that does not necessarily mean that the project will become a reality, with all of the strings Emanuel has attached.

The mayor has ruled out even a penny of taxpayer support. He wants trips to take 20 minutes or less, with express trains operating every 15 minutes for 20 hours a day.

And he wants the system bankrolled exclusively by project revenues — fares, advertising and transit-oriented development — while also demanding that fares remain reasonable.

“We think they can do it with premium fares that are significantly lower than Uber, Lyft and taxis,” Rivkin said Tuesday.

Joseph Schofer, professor of civil and environmental engineering at Northwestern University, has accused Emanuel of “defining a very narrow path” for success by tacking on too many conditions.

“It seems like they’re asking for a lot and the city is not taking any risk at all,” Schofer has said.

Schofer has also questioned whether there is enough demand to make a privately built express train to O’Hare a self-sustaining, “profit-making operation.”

He has noted that Toronto opened a high-speed rail line before the 2015 Pan Am Games that struggled so hard to reach ridership goals that the $27.50 fare had to be cut in half.

Rivkin strongly disagreed.

“O’Hare is not standing still. … If the City Council agrees with our vision, O’Hare will be growing. And as O’Hare grows, the capacity to access O’Hare needs to grow,” he said.

Musk has previously outlined his vision for a tunnel network under Los Angeles, in which cars would park on high-speed sleds, then be whisked along underground tracks.

Elaborating on his idea for Chicago, he tweeted last fall, “Electric pods for sure. Rails maybe, maybe not.”

Meridiam is a Paris-based global investor and asset manager that last year raised $1.2 billion for a fund dedicated to bankrolling “long-term investments in North American public infrastructure projects” with a particular focus on investing in “sustainable and climate-resilient assets.”

Its projects include a tunnel at the Port of Miami, a terminal at New York’s LaGuardia Airport, California’s Presidio Parkway and a light rail project in Maryland.

JLC is an infrastructure fund launched last year by former NBA great Magic Johnson and Chicago’s Jim Reynolds, CEO of Loop Capital Markets. The fund has set aside “millions” to bankroll future projects and has already put its money behind construction of a new terminal at Denver International Airport.

Antartica Capital is a New-York-based global investment firm that targets infrastructure with a particular focus on “identifying investment opportunities that offer potential for operational value creation.”

Mott MacDonald served as design engineer for a terminal at London’s Heathrow Airport, for the United Kingdom’s largest court complex and for Mosaic Stadium, home of the CFL’s Saskatchewan Rough Riders.

The city has identified three possible routes: the CTA Blue Line that runs along the median of the Kennedy Expressway; the Metra North Central line that comes into downtown just north of Union Station; and freight railroad rights-of-way that would run west to Forest Park and north to O’Hare.