New York to DC in half an hour.

Elon Musk — the serial entrepreneur who heads Tesla (TSLA), SpaceX and now The Boring Company — says he “just received verbal [government] approval” to build a new underground hyperloop network that can shuttle commuters between the two cities in 29 minutes.

He made the announcement on Twitter, declaring his new super-fast transportation network will also have stops in Philadelphia and Baltimore, as well as “up to a dozen or more entry/exit elevators in each city.”

The announcement sparked lots questions: Musk didn’t say what government official gave him a “verbal” OK for the project, and it’s not clear that anyone would have the ability to sign off on such a project single handedly, much less verbally. Moreover, acquiring all the state and local permits necessary to build a hyperloop would undoubtedly be a complex, time consuming task.

Neither The Boring Company or the Department of Transportation responded immediately to a request for comment.

And even if the ultra-high speed rail does receive all the required approvals, it’s not clear who would build it.

While the hyperloop is Musk’s idea, he hasn’t taken on the project personally. Rather, he challenged other inventors to create it — and a couple of companies have cropped up to tackle the challenge, most notably, Hyperloop One.

Related: All the quirky details you need to know about Elon Musk’s Boring company

But the New York-DC hyperloop could also be the first major project for Musk’s tunnel-digging company, The Boring Company. He established the firm earlier this year to build an underground web of tunnels beneath Los Angeles, through which cars can travel up to 130 miles per hour on metal skates.

That’s a different concept than the hyperloop, which is meant for long-distance traveling and is intended to have much higher top speeds.

So far, The Boring Company has spawned many puns, but not much progress in terms of reaching Musk’s goal.

Musk said during a TED conference in April that his tunneling company ties in closely with the hyperloop, since both require vacuum-sealed tunnels.

He actually mentioned an East Coast hyperloop at that conference, saying “If you were to do something like a DC-to-New York hyperloop, I think you’d probably want to go underground the entire way because it’s a high-density area.”

Musk added that his tunnel digging process wouldn’t disturb people above ground.

“You’re going under a lot of buildings and houses, and if you go deep enough, you cannot detect the tunnel,” he said.

One tweet Musk sent Thursday hinted that his boring company will dig the tunnel from New York to DC. He said he’ll start the project “in parallel” with the LA tunnel network. But he didn’t go so far as to say who will install the hyperloop.

Musk tweeted about even bigger ambitions to build a hyperloop between Los Angeles and San Francisco and another in Texas.

Both hyperloop and Musk’s LA tunneling idea are longshot ideas — but Musk does have a flare for bringing the impossible to life.

CNNMoney (New York) First published July 20, 2017: 12:11 PM ET