NASA on Thursday awarded three companies contracts to build spacecraft capable of landing humans on the moon, sparking a new space race that NASA hopes will propel the United States back to the lunar surface for the first time since 1972.

Blue Origin, the space outfit owned by Jeff Bezos; Dynetics, a subsidiary of Leidos, a Reston, Va.-based information technology firm; and Elon Musk’s SpaceX won contracts, giving NASA three options that would compete against each other as NASA scrambles to meet an ambitious White House mandate to put humans on the moon by 2024. (Bezos owns The Washington Post.)

Boeing, typically among NASA’s key contractors but whose space program has experienced multiple setbacks and delays, also submitted a bid but was not selected.

In an interview with The Washington Post, NASA Administrator Jim Bridenstine said he remains confident NASA will be able to meet the 2024 deadline, even though the first flight of the Space Launch System, the Boeing-built rocket that would launch astronauts to the moon, will be pushed back again, this time to November 2021.

Still, the announcement of contracts for the landers — the first lunar spacecraft contracts NASA has awarded since the 1960s’ Apollo era — is a significant step toward getting the U.S. crews to the moon quickly and building what NASA hopes will become a permanent presence on the moon’s surface.

A lunar landing is “starting to feel very, very real,” Bridenstine said. “It’s very exciting. There have been lots of attempts to go back to the moon since 1972, but none have materialized.”

It’s not clear yet, however, that NASA’s latest effort, dubbed “Artemis” after the twin sister of Apollo, will materialize, either.

To give itself a better shot at pulling off the feat by 2024, NASA has changed its plans. Initially NASA was going to fly its astronauts to an outpost in orbit around the moon, known as the Gateway. From there, they would descend to the lunar surface. But now NASA says that while it remains committed to the Gateway for the long term, it will likely not use it for the next moon landing.

Instead it intends to fly astronauts in the Orion spacecraft, built by Lockheed Martin, to lunar orbit, where it would meet up and dock with the lander, which would take them to the moon’s surface. Still, NASA officials said, the plan could change.

For a moon landing to become a reality, however, NASA and the White House must sell their plan to a skeptical Congress, which has not yet signed off on a program projected to cost $35 billion through 2024. NASA and Boeing, the prime contractor on the SLS program, also must make significant progress on the rocket. A recent Government Accountability Office report said that despite years of development, the rocket “may develop leaks when it is filled with fuel.” Another recent report, by the agency’s inspector general, said the total cost of the SLS, Orion spacecraft and associated ground systems could be as much as $50 billion.

NASA also is struggling to get to the moon under a drastically expedited timeline. Initially it was planning to land humans on the moon by 2028. But Vice President Pence last year directed the space agency to do it by 2024 “by any means necessary.”

Despite the many challenges, the plan is attainable, Douglas Loverro, NASA’s head of human spaceflight, said in an interview.

“This is a first giant step, but it’s only the first step,” he said. “We have so much work ahead of us. Now the hard part begins. And it’s going to take the best of NASA and the best of industry to get there.”

NASA officials declined to comment on Boeing’s absence from the list. The loss for the aerospace behemoth comes as it has struggled not only with the SLS rocket, but with the Starliner spacecraft it is developing to fly NASA astronauts to the International Space Station in low Earth orbit. A recent test mission without crews onboard went so badly that the company decided to refly the flight.

For Blue Origin, the contract award is a major victory. Founded in 2000 by Bezos, the company has for years been urging the space agency to return to the moon, specifically the south pole, where scientists have discovered water in the form of ice.

Blue has been pitching its lander, called Blue Moon, since 2017, and Bezos has said he would invest heavily in it himself. Last year, Blue Origin announced it was teaming up on the project with Lockheed Martin, Northrop Grumman and Draper — “a national team for a national priority,” Bezos said. “This is the kind of thing that’s so ambitious that it needs to be done with partners. This is the only way to get back to the moon fast. We’re not going back to the moon to visit. We’re going back to the moon to stay.”

Bob Smith, Blue Origin’s CEO, said at a news conference that the effort would “humbly stand on the shoulders of Apollo. … I know I speak for many on our team that going to the moon is the reason why we got into this business, and we couldn’t be more excited about that."

NASA said that Blue Origin was furthest along with its project and awarded it the largest award, $579 million. Dynetics, which has paired with the Sierra Nevada Corp., would receive $253 million and scored the highest marks, according to NASA’s source selection document. SpaceX, which bid its Starship spacecraft, won $135 million. The contracts are for the first stage of the program and would last through February 2021. After that, NASA could decide whether to proceed with all three partners or chose two of the three.

The award was the latest in a string of wins for SpaceX, which is poised to fly NASA’s astronauts to the space station on May 27. NASA had previously awarded SpaceX a contract, worth as much as $7 billion, to resupply the Gateway with cargo.

During the news conference Musk said the announcement would ultimately help move humanity into deep space. “I think we’ve got potential for an incredibly exciting future in space, with a base on the moon and ultimately sending people and having a self-sustaining city on Mars,” he said.

While the Gateway likely won’t be used for the next lunar landing, Bridenstine said the agency is “100 percent committed to the Gateway. That being said, we are also committed to going as fast as possible.”

Bridenstine said SpaceX’s Falcon Heavy rocket could be used to launch the habitat and power and propulsion elements of an orbiting space station after they are assembled on the ground.

Though the astronauts would only be on the surface of the moon for a number of days, as in Apollo, the goal would be to study the region around the moon’s south pole to help NASA set up a permanent presence there. NASA is particularly interested in the ice discovered in the perpetually shadowed craters, and how it could be used to sustain life and even be converted into rocket fuel.

“I view this as learning to fly to the moon again and learning the right way so we can do it again and again,” Loverro said. “This is not a flash in the pan. It is the first step of many steps we’re going to take there.”