Shortly after losing communication with NASA, the Artemis II crew is making its closest approach to the moon.

Orion will be about 4,070 miles above the surface of the moon, according to NASA.

The Artemis II astronauts will be the first humans to see most of the far side of the moon, or the side not visible from Earth, since the Apollo missions.

"It turns out there's about 60% of the far side, I think, that has never been seen by human eyes because of the lighting conditions," Reid Wiseman, mission commander, said during a news conference on March 29. "Apollo always wanted that light on the front side of the moon for their landing and launch capability. ... We've seen it in satellite photos, but humans have never, ever seen that before. That's cool."

The Artemis II crew has reached the far side of the moon and has entered a communications blackout, NASA said.

The federal space agency said the communications blackout is planned and should last for about 40 minutes as Orion passes behind the moon.

The moon blocks the radio signals needed for Mission Control to maintain contact with Orion via the Deep Space Network, which is NASA's international array of giant radio antennas that supports interplanetary spacecraft missions.

NASA has said the Artemis II crew will now make its closest approach to the moon at 7:00 p.m. ET and will reach its furthest distance from Earth at 7:02 p.m. ET.

Previously, the crew was supposed to make its closest approach at 7:02 p.m. ET and reach maximum distance from the Earth at 7:07 p.m. ET.

-ABC News' Briana Alvarado

The Artemis II crew's historic lunar flyby began around 2:45 p.m. ET.

The flyby, which should take around seven hours, will see the Orion spacecraft be close enough to the moon for the crew "to make detailed observations of geologic features on the lunar surface," according to NASA.

NASA said coverage will include live views of the moon taken by cameras that are mounted on Orion's solar arrays.

At a press conference following the safe splashdown of the Artemis II crew in the Pacific Ocean on Friday evening, NASA officials hailed the historic 10-day mission and said bigger challenges lie ahead.

"So, ya'll, we did it," said Lori Haze, deputy associate administrator for NASA’s Exploration Systems Development Mission Directorate.

Howard Hu, NASA Orion program manager, said: "This is the start of a new era of human space exploration."

By 2028, NASA plans to land a crew on the surface of the moon with the Artemis IV mission.

Amit Kshatriya, associate NASA administrator, said the successful ending of the mission means "the path to the lunar surface is open," but hard work remains ahead.

"Fifty-three years ago, humanity left the moon. This time we returned to stay," Kshatriya said. "Let us finish what they started ... Let us not go to plant flags and leave -- but to stay."