A rendering of one idea for an O'Hare express rail depot at the airport View Full Caption City of Chicago

O'HARE — Mayor Rahm Emanuel's plan for a high-speed rail line between Downtown and O'Hare Airport got a jolt of electricity Monday with the news that Tesla founder Elon Musk may be interested in the project that the mayor has called "essential for the city's future."

Musk, who also founded SpaceX — which hopes to transport astronauts to the International Space Station — met with a team from the mayor's office in Los Angeles recently about Musk's drilling firm, the Boring Co., which may bid to build a nonstop underground rail line, Emanuel said Monday afternoon.

"[Musk] has expressed an interest in what Chicago is doing," Emanuel said. "It would be a tremendous investment and job creator, an economic engine for the city that would pay dividends for decades ahead."

Emanuel said he had invited Musk's team to visit Chicago to see whether a tunnel makes sense for the O'Hare express train.

"The opportunity for the City of Chicago is endless and boundless," Emanuel said, adding that it would benefit the Loop and airports. "I'm very excited about their interest."

In 2016, Emanuel announced plans to pay $2 million to the Parsons Brinckerhoff design firm to come up with ideas for where Downtown and O'Hare stations might be located and the best and quickest route through the city.

Results of that effort have not been announced. It is unclear how much the project would cost, or how it would be paid for.

Several aldermen and transportation experts have been critical of the push for an express train to the airport, which already is connected to the Loop by the CTA Blue Line, which is itself in the midst of a $492 million renovation.

Musk's interest in the O'Hare high-speed rail line was first reported by Crain's Chicago Business.

Musk's firm has developed a tunnel-drilling technology designed to cut construction costs by at least 90 percent by using drilling technology it invented to bore narrow tunnels.

Musk's ability to drill narrow tunnels may be crucial to avoid disrupting the Blue Line tracks, the Metra tracks or the Kennedy Expy. — not to mention city neighborhoods.

Tickets on an express train — which would zoom from O'Hare to Downtown in 20 to 25 minutes — could cost $25 to $40, according to estimates, while a one-way fare on the Blue Line from O'Hare now costs $5.

Koch told Crain's that Musk discussed a train featuring passenger cars smaller than CTA "L" cars that would leave as they fill up and travel at 125 mph. Musk also has touted a near-supersonic Hyperloop transport concept that could send passenger cars hurtling at 600 mph using vacuum pressure.

The Boring Co. is digging a tunnel from Los Angeles International Airport to Santa Monica, one of the worst stretches of Los Angeles' always-clogged 405 freeway.

The city could ask firms — including Musk's company — to bid on the project by the end of the year, officials said.