Sunita Williams among 9 astronauts to fly SpaceX, Boeing commercial-rockets

"Today, America's dreams of greater achievements in space are within our grasp," said NASA Administrator Jim Bridenstine.

Eight NASA astronauts and one former astronaut-turned-corporate crew member will launch on Boeing CST-100 Starliner and SpaceX Dragon capsules to International Space Station beginning in 2019.

The missions will mark the first crewed launches from US soil since the end of the space shuttle program in 2011.

NASA has worked closely with the companies throughout design, development, and testing to ensure the systems meet all requirements.

"The astronauts we assign to these first-flights are at the forefront of this exciting new time for human spaceflight," said Mark Geyer, Director of NASA's Johnson Space Center in Houston.

"It will be thrilling to see our astronauts lift off from American soil," Geyer said.

Josh Cassada, 45, will fly with Sunita Williams, 52, aboard NASA's first contracted Starliner mission. It will be Cassada's first spaceflight. Williams previously logged 321-days in orbit on two stays aboard the space station, most recently returning to the Earth in 2012.

The commercial crew members took to the stage during an event led by Bridenstine at the agency's Johnson Space Center in Houston.

NASA astronauts Robert Behnken, 48, and Douglas Hurley, 51, will fly together as SpaceX's first Dragon crew.

Veterans of two spaceflights each, Behnken and Hurley will lift off atop a SpaceX Falcon 9 rocket from the Kennedy Space Center's Pad 39A, the same Florida launch pad where the space shuttle left Earth for the last time in July 2011 with Hurley as the pilot.

NASA astronauts Eric Boe, 53, and Nicole Mann, 41, will join former astronaut and now Boeing executive Christopher Ferguson, 56, as the crew of the Starliner test-flight, launching atop a United Launch Alliance Atlas V rocket at the Cape Canaveral Air Force Station, Florida.

Ferguson had flown in three shuttle missions as NASA astronaut. Boe piloted two shuttle-flights. This will be Mann's first launch.

Victor Glover, 42, and Michael Hopkins, 49, will fly on the first operational mission of SpaceX's crewed Dragon. It will be Glover's first time in space. Hopkins logged 166 days aboard the space station in 2014.

In addition to these nine, NASA also announced the four astronauts who will fly aboard the first operational Starliner and Dragon missions to the space station.