Mayor Rahm Emanuel could have a powerful ally in his drive to realize the elusive dream of building a high-speed rail line between downtown and O’Hare Airport: President Donald Trump.

Trump may be bashing Chicago on an almost daily basis for its skyrocketing murder rate. But, he’s a big fan of airport express service.

Aviation Commissioner Ginger Evans said she was delighted to hear that during a White House meeting Thursday that focused on the president’s plan to cut taxes and regulations impacting airports and the airline industry.

“He’s obviously very well-traveled. And he mentioned that he’s seen and ridden on some very high-performance, high-speed trains in other countries,” Evans said.

“And he said, ‘It’s just staggering to me that several of these countries have multiple high-speed trains and we don’t even have one.’ I’ve been saying that for years. Can’t we have just one? When you go these other countries, you’re like, ‘My gosh. Of course we want this. Of course we should have this.’”

Evans was asked whether Trump could do anything to speed the way for an O’Hare express train that has been a dream of Chicago mayors for decades.

“He’s very committed to infrastructure generally. That’s very clear. He did make that one mention that he wanted a high-speed rail project somewhere,” she said.

Earlier this week, Emanuel vowed to forge ahead with the O’Hare express project within three years.

The mayor said the city has been “hearing from potential investors and companies from around the world about their interest in this project” and that its engineers “have made progress in identifying the routes to move this forward.”

The mayor also announced that the city is retaining Bob Rivkin, who served as general counsel under Emanuel’s long-time friend, former U.S. Transportation Secretary Ray LaHood, to provide “legal expertise in identifying a clear path forward and working with potential partners.”

On Friday, Evans said engineering and design giant WSP Parsons Brinckerhoff is continuing to study “five different routes” for the new service.

She acknowledged that the Kennedy Expressway corridor is still on the list. But, she refused to identify the other routes on grounds that some are privately owned and, “We don’t want to negotiate in public.” But, she ruled out the tracks around Union Station as “not viable.”

 “It’s over-capacity. There are several higher priority demands for space at Union Station. I met with them early on and it’s just not a good idea for us to co-mingle with Amtrak. They own that station. Their needs come first. … They don’t have space for anything there,” she said.

After ruling out the Block 37 super-station that former Mayor Richard M. Daley spent more than $200 million to build, Evans refused to say where the downtown station would be located. That depends on the route.

“Some of them might need a new station. Some of them might be able to take a modification of an existing station. Which each one of those routes would require is something that will be taken into account in both the cost and ridership estimates,” the commissioner said.

Whatever happens, the new system would be, what Evans called a “turn-key” operation. The city would only be responsible for providing the “on-airport” station, but not the downtown station.

Everything else would be turned over to a private entity that would make its money, in part, by charging a premium fare — in the $25-to-$35 range — for express service that would whisk them between downtown and O’Hare in 20 or 25 minutes. That’s roughly half the time it takes to take the Blue Line.

“They would design, build, finance and operate. … There are lots of people around the world who do systems like that. Lots of different entities,” Evans said.

Pressed to describe where those private investors would get their returns other than fares, Evans said, “A combination of development opportunities at stations, advertising, services, selling food and beverage. There’s always a blended revenue offering.”