Two NASA astronauts safely boarded the International Space Station on Sunday, capping a successful flight of SpaceX's historic Crew Dragon Demo 2 mission.

The capsule connected to the station at 10:16 a.m. EDT, slightly ahead of the scheduled time as the space station passed above the northern China-Mongolia border. Astronauts Doug Hurley and Bob Behnken entered the station at 1:22 p.m.

NASA and SpaceX crews on the ground congratulated the astronauts, while astronaut Chris Cassidy -- already on board the station -- welcomed them.

"Bob and Doug, we here at SpaceX are honored to have been part of the ushering in of this new era of human spaceflight," SpaceX engineer Anna Menon said.

Behnken, in turn, congratulated the teams at SpaceX and NASA.

"Their incredible efforts over the last several years to make this possible cannot be overstated," he said of the SpaceX employees.

Just before docking, practiced flying the capsule manually. He congratulated SpaceX's teams for successfully training him and building the capsule.

"It flew really well, very crisp," Hurley said.

Behnken joked about Hurley's brief manual piloting experience.

"I only had to twist Doug's arm for two or three times to get him to allow me to deactivate the piloting controls," Behnken said.

The mission lifted off from NASA's Kennedy Space Center in Florida on Saturday afternoon -- the first crewed launch from U.S. soil in nine years.

The successful 19-hour journey to the space station makes SpaceX the first private company to send astronauts into orbit. It also was the first time since the final space shuttle mission that NASA didn't have to rely on Russia to get people into space.

After the launch on Saturday, Musk said he considers the launch a boost for SpaceX's ultimate goal of traveling to Mars. The company has been testing prototypes of its next-generation rocket and habitat, Starship, in Texas.

"This is hopefully the first step on a journey toward a civilization on Mars, of life becoming multi-planetary," Musk said. "That's seeming increasingly real after what happened today, getting people to orbit, finally after 18 years."

The astronauts slept for about eight hours before the approach to the space station.

No issues with the spacecraft have been reported -- described by a SpaceX commentator as "pretty boring for the astronauts, but that's what we wanted.

NASA Administrator Jim Bridenstine said the launch proved that NASA's new approach of contracting with private companies for entire missions is successful.

"America is leading again in space," Bridenstine said.

SpaceX secured a contract to provide ferry service to the space station for a fixed cost in 2014, and developed the rocket and capsule with NASA's cooperation.

The Falcon 9 rocket had already been proven as a reliable workhorse for carrying supplies to the space station 250 miles above Earth in 20 flights.

The space station travels at more than 17,000 mph, so the capsule performed several orbits to match its speed and altitude. The capsule docked autonomously.

Behnken and Hurley don't know how long they will be on the space station.

NASA has said it could be as little as six weeks and as much as 16 weeks, depending on how quickly the crew completes necessary maintenance on the space station and how favorable weather conditions are for spacecraft splashdown.

Behnken is scheduled to make several spacewalks with Cassidy, as Hurley monitors and controls instruments inside the station.

If the mission ultimately is successful, NASA plans to launch another SpaceX capsule to the space station Aug. 30, Bridenstine said.

Crew members for that mission are to be NASA astronauts Mike Hopkins, Victor Glover and Shannon Walker, along with Soichi Noguchi, an astronaut with the Japan Aerospace Exploration Agency.

Over the past decade, NASA astronauts only used Russian Soyuz rockets and capsules to reach the space station, at a cost of more than $70 million per seat.

Behnken, 49, and Hurley, 53, have been astronauts since their selection in 2000. They worked closely with SpaceX to develop the new spacecraft systems.

The return to Earth for the Demo 2 mission would mark the first splashdown of a U.S. space capsule carrying astronauts since the Apollo-Soyuz Test Project in 1975.

Astronauts return to space from U.S. soil

A SpaceX Falcon 9 rocket lifts off seconds after 3:22 p.m. with the first manned Crew Dragon spacecraft from Complex 39A at the Kennedy Space Center in Florida on May 30, 2020. The mission, classified as Crew Demo 2, is flying NASA astronauts Doug Hurley and Bob Behnken and is the first manned mission from the United States in more than nine years.Photo by Joe Marino/UPI | License Photo

A SpaceX Falcon 9 rocket lifts off seconds after 3:22 p.m. with the first manned Crew Dragon spacecraft from Complex 39A at the Kennedy Space Center in Florida on May 30, 2020. The mission, classified as Crew Demo 2, is flying NASA astronauts Doug Hurley and Bob Behnken and is the first manned mission from the United States in more than nine years.Photo by Joe Marino/UPI | License Photo

A SpaceX Falcon 9 rocket lifts off seconds after 3:22 p.m. with the first manned Crew Dragon spacecraft from Complex 39A at the Kennedy Space Center in Florida on May 30, 2020. The mission, classified as Crew Demo 2, is flying NASA astronauts Doug Hurley and Bob Behnken and is the first manned mission from the United States in more than nine years.Photo by Joe Marino/UPI | License Photo

People on Cocoa Beach watch as NASA astronauts Bob Behnken and Doug Hurley lift off from Kennedy Space Center's Pad 39-A onboard SpaceX Demo-2 Falcon 9 and the Crew Dragon to the International Space Station. Liftoff of Falcon 9 was the second attempt and came on on May 30, 2020. Photo By Gary I Rothstein/UPI | License Photo

First NASA Crew Departs For Historic Launch from Space CenterNASA Astronauts Doug Hurley (L) and Bob Behnken depart the Neil A. Armstrong Operations and Checkout Building at Kennedy Space Center in Florida on May 30, 2020. The two astronauts will ride in Tesla Model X vehicles to Launch Complex 39A, where they will board the SpaceX Crew Dragon spacecraft and fly on the first manned launch from the United States in more than nine years.Photo by Joe Marino/UPI | License Photo

NASA Astronaut Bob Behnken gives a thumbs up following walkout from the Neil A. Armstrong Operations and Checkout Building at the Kennedy Space Center in Florida on May 30, 2020. Behnken will fly on the first launch of the manned Crew Dragon spacecraft to the International Space Station with astronaut Doug Hurley. Photo by Joe Marino/UPI | License Photo

A SpaceX Crew Dragon spacecraft and Falcon 9 rocket stand on Launch Complex 39A on May 29, 2020, prepared for the launch of the first manned mission for NASA from the Kennedy Space Center in Florida in more than nine years. NASA and SpaceX will try a second attempt at launching astronauts Doug Hurley and Bob Behnken on the Crew Demo 2 mission on May 30. Photo by Joe Marino/UPI | License Photo

A SpaceX Crew Dragon spacecraft and Falcon 9 rocket stand on Launch Complex 39A on May 29, 2020, prepared for the launch of the first manned mission for NASA from the Kennedy Space Center in Florida in more than nine years. NASA and SpaceX will try a second attempt at launching astronauts Doug Hurley and Bob Behnken on the Crew Demo 2 mission on May 30. Photo by Joe Marino/UPI | License Photo

NASA Astronauts Doug Hurley (L) and Bob Behnken depart the Neil A. Armstrong Operations and Checkout Building at Kennedy Space Center in Florida on May 30, 2020. The two astronauts will ride in Tesla Model X vehicles to Launch Complex 39A, where they will board the SpaceX Crew Dragon spacecraft and fly on the first manned launch from the center in more than nine years. Photo by Joe Marino/UPI | License Photo

NASA Astronaut Doug Hurley waves to his family following walkout from the Neil A. Armstrong Operations and Checkout Building at the Kennedy Space Center in Florida on May 30, 2020. Hurley will fly on the first NASA SpaceX mission in the Crew Dragon spacecraft to the International Space Station with astronaut Bob Behnken. Photo by Joe Marino/UPI | License Photo

A SpaceX Falcon 9 rocket vents fuel after NASA and SpaceX mnagement called a hold to the launch at the Kennedy Space Center in Florida on May 27. Photo by Joe Marino/UPI | License Photo

Hans Koenigsmann, vice president for build and flight reliability at SpaceX, looks at a monitor showing a live feed of a SpaceX Falcon 9 rocket carrying the company's Crew Dragon spacecraft on the launch pad during the countdown for a launch attempt of NASA's SpaceX Demo-2 mission. Photo by Joel Kowsky/NASA | License Photo

Spectators leave Cocoa Beach after the mission was scrubbed with minutes left on the countdown. Photo By Gary I Rothstein/UPI | License Photo

NASA astronauts Robert Behnken (L) and Douglas Hurley are seen in the crew access arm at Launch Complex 39A on May 27. They were strapped into the Crew Dragon capsule when weather forced a postponement of the launch. Photo courtesy of SpaceX | License Photo

From left to right, Kennedy Space Center Director Bob Cabana, second lady Karen Pence, Vice President Mike Pence, first lady Melania Trump, President Donald Trump, Marillyn Hewson, Chief Executive Officer of Lockheed Martin, Mike Hawes, VP of Human Space Exploration and Orion Program Manager at Lockheed Martin Space, and NASA Administrator Jim Bridenstine stop by the Artemis I capsule during a tour of the Neil A. Armstrong Operations and Checkout Building. Photo by Bill Ingalls/NASA | License Photo

Trump participates in a SpaceX Demonstration Mission 2 launch briefing following the departure of NASA astronauts to board a SpaceX Crew Dragon spacecraft for launch. Photo by Bill Ingalls/NASA | License Photo

Hurley (L) and Behnken, wearing SpaceX spacesuits, prepare to depart the operations building for Launch Complex 39A to board the SpaceX Crew Dragon spacecraft. Photo by Bill Ingalls/NASA | License Photo

From left to right, SpaceX owner and chief engineer Elon Musk, Bridenstine, Mike Pence and Karen Pence applaud the astronauts as they head to the spacecraft. Photo by Bill Ingalls/NASA | License Photo

Hurley (L) and Behnken give their families virtual hugs as they prepare for the Demo-2 mission launch. Photo by Bill Ingalls/NASA | License Photo

Hurley boards a Tesla Model X for the ride to the launch area. Photo by Joe Marino/UPI | License Photo

A SpaceX Crew Dragon spacecraft and Falcon 9 rocket lie horizontally on Complex 39A on May 26. Photo by Joe Marino/UPI | License Photo

The Vehicle Assembly Building is seen at sunset as preparations continue for the NASA's SpaceX Demo-2 mission on May 25. Photo by Joel Kowsky/NASA | License Photo

In this black-and-white infrared image, a SpaceX Falcon 9 rocket with the company's Crew Dragon spacecraft onboard is seen on the launch pad. Photo by Joel Kowsky/NASA | License Photo

View of the crew access arm in position with the Crew Dragon spacecraft and the SpaceX Falcon 9 rocket on May 24. Photo courtesy of SpaceX | License Photo

Behnken and Hurley are seen on a monitor showing inside the Crew Dragon capsule at Launch Complex 39A during a dress rehearsal on May 23. Photo by SpaceX/UPI | License Photo

Hurley (L) and Behnken participate in a dress rehearsal for launch at the agency's Kennedy Space Center in Florida on May 23. NASA Photo by Kim Shiflett/UPI | License Photo

Behnken rehearses putting on his SpaceX spacesuit in the Astronaut Crew Quarters. Photo by Kim Shiflett/NASA | License Photo

Hurley and Behnken return to the Neil A. Armstrong Operations and Checkout Building from Launch Complex 39A after completing the dress rehearsal. Photo by Bill Ingalls/NASA | License Photo

Norm Knight, deputy director of Flight Operations at NASA's Johnson Space Center (L), and Steve Stich, deputy manager of NASA's Commercial Crew Program (R), monitor the countdown during the dress rehearsal. Photo by Joel Kowsky/NASA | License Photo

Hurley (L) and Behnken depart the Neil A. Armstrong Operations and Checkout Building for Launch Complex 39A. NASA Photo by Bill Ingalls/UPI | License Photo

NASA and SpaceX managers participate in a flight readiness review for the upcoming Demo-2 launch in the Operations Support Building II at NASA's Kennedy Space Center on May 21. Photo by Kim Shiflett/NASA | License Photo

A SpaceX Falcon 9 rocket with the Crew Dragon spacecraft onboard is seen as it is rolled out of the horizontal integration facility at Kennedy as preparations continue for the Demo-2 mission on May 21. Photo by Bill Ingalls/NASA | License Photo

The rocket is raised into a vertical position on the launch pad as preparations continue for the Demo 2 mission, scheduled to launch at 4:33 p.m. EDT on May 27. Photo by Bill Ingalls/NASA | License Photo

From left to right, Behnken and Hurley pose with NASA Administrator Jim Bridenstine and Kennedy Space Center director Bob Cabana after the astronauts' arrival at the space center in Florida on May 20. Photo by Joe Marino/UPI | License Photo

The two astronauts arrived to be the first crew to launch from the Kennedy Space Center on the SpaceX Crew Demo spacecraft. Photo by Joe Marino/UPI | License Photo

Hurley speaks to the media following his arrival at the Kennedy Space Center. Photo by Joe Marino/UPI | License Photo

The SpaceX Crew Dragon spacecraft arrives at Launch Complex 39A at NASA's Kennedy Space Center in Florida, transported from the company's processing facility at Cape Canaveral Air Force Station on May 15. Photo by Kim Shiflett/NASA | License Photo

The SpaceX Crew Dragon spacecraft that will be used for the Crew-1 mission for NASA's Commercial Crew Program undergoes processing inside the clean room at SpaceX headquarters in Hawthorne, Calif. Photo courtesy of SpaceX | License Photo

Behnken (L) and Hurley successfully completed a fully integrated test of Crew Dragon's critical flight hardware at a SpaceX processing facility on Cape Canaveral Air Force Station in Florida on March 30. Photo courtesy of SpaceX | License Photo

NASA and SpaceX completed an end-to-end demonstration of the teams' ability to safely evacuate crew members from the fixed service structure during an emergency situation at Launch Complex 39A on April 3. Photo courtesy of SpaceX | License Photo

The SpaceX Crew Dragon spacecraft undergoes final processing at Cape Canaveral Air Force Station in Florida. Photo courtesy of SpaceX | License Photo

Hurley examines the critical flight hardware during the test on March 30. Photo courtesy of SpaceX | License Photo

Hurley (R) and Behnken participate in SpaceX's flight simulator. Photo courtesy of SpaceX | License Photo

SpaceX teams executed a full simulation of launch and docking of the Crew Dragon spacecraft, with Hurley (R) and Behnken participating in SpaceX's flight simulator on March 19 and 20. Photo courtesy of SpaceX | License Photo

SpaceX's Crew Dragon capsule completes acoustic testing in Florida ahead of its crewed flight to and from the ISS later this year. Photo courtesy of SpaceX | License Photo

Hurley (L) and Behnken stand near Launch Pad 39A during a dress rehearsal ahead of the SpaceX uncrewed In-Flight Abort Test at Kennedy Space Center, Fla., on January 17. In the background, the company's Falcon 9 rocket is topped by the Crew Dragon spacecraft. The flight test will demonstrate the spacecraft's escape capabilities in preparation for crewed flights to the International Space Station. Photo by Kim Shiflett/NASA | License Photo

NASA Administrator Jim Bridenstine (L) and SpaceX chief Elon Musk converse at Kennedy Space Center's launch control center while awaiting liftoff of a SpaceX Falcon 9 rocket and Crew Dragon spacecraft on the uncrewed in-flight abort test on January 19. Photo by Kim Shiflett/NASA | License Photo

Hurley (R) and Behnken don SpaceX spacesuits in the astronaut crew quarters during a dress rehearsal ahead of the company's uncrewed in-flight abort test. Photo by Kim Shiflett/NASA | License Photo

The test, which did not have NASA astronauts aboard, demonstrated Crew Dragon's ability to reliably carry crew to safety in the unlikely event of an emergency on ascent. Photo courtesy of SpaceX | License Photo

A SpaceX Falcon 9 rocket boosts the Crew Dragon spacecraft for NASA on a launch abort test from Complex 39A at Kennedy on January 19. SpaceX conducted the test as a final measure to assure safety for future crewed missions to the International Space Station. Photo by Joe Marino-Bill Cantrell/UPI | License Photo

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