The three pioneers will help restore American access to space from USA soil, a capability that ended when the shuttle was retired seven years ago.
"This is a big deal for our country and we want America to know that we are back, that we are flying American astronauts on American rockets from American soil", Bridenstine said in Houston.
"To work and live in space is just a humbling and unbelievable blessing in and of itself, and now to have the opportunity to work with these great companies on something that is so important to our nation and to NASA", Glover said.
The Starliner test flight astronauts named by the agency are Eric Boe, Christopher Ferguson, and Nicole Aunapu Mann, while the Crew Dragon test flight astronauts would be Robert Behnken and Douglas Hurley. He flew on Space Shuttle Endeavour in 2008 with fellow Georgia Tech graduates Sandy Magnus and Shane Kimbrough.
USA astronauts have been relying on Russian capsules to travel to the space station, with each seat costing NASA as much as $82 million (€71 million). Boeing will launch its CST-100 Starliner on top of a United Launch Alliance Atlas V rocket at Cape Canaveral Air Force Base, also in Florida.
Last week, Boeing confirmed that it had a problem with its launch abort system, which is created to ferry crews to safety in the event of an emergency.
Since then, they have been in a race to see which company would fly first in what's become a sort of modern-day space race.
NASA assigns astronauts to first commercial crew missions
The first Boeing Starliner mission to the ISS will be crewed by John Cassada, a NASA astronaut, physicist and Navy test pilot.
NASA's partners on the International Space Station program - the Russian space agency Roscosmos, the European Space Agency, the Japan Aerospace Exploration Agency, and the Canadian Space Agency - are expected to assign members of their own astronaut corps to the CST-100 and Crew Dragon crew rotation flights. For the first actual Crew Dragon mission, Victor Glover will undertake his first spaceflight alongside seasoned astronaut Michael Hopkins, who has spent 166 days aboard the space station.
NASA's Commercial Crew Program is facilitating the development of a US commercial crew space transportation capability with the goal of achieving safe, reliable and cost-effective access to and from the International Space Station and low-Earth orbit.
For the past seven years, Nasa astronauts have hitched rides to the orbiting outpost on Russia's Soyuz spacecraft - at a cost of some US$80 million a seat. The missions will likely include veterans from the US' Space Shuttle program, Gizmodo reported.
For Crew Dragon, the now confirmed crew includes Navy commander, aviator, and test pilot Victor Glover.
Glover joined the astronaut corps in 2013; he is a U.S. Navy commander and test pilot with nearly 3,000 flight hours logged in more than 40 different aircraft. Ms. Williams previously logged 321 days in orbit on two stays aboard the space station, most recently returning to the Earth in 2012.
In total, NASA explained "to have signed a contract for six missions, with a maximum of four astronauts per mission, for each company". In 2013 and 2014, Hopkins spent almost six months aboard the ISS, logging almost 13 hours of spacewalks.
"Both contractors have said that their schedules are aggressive and they set ambitious-rather than realistic-dates, only to frequently delay them", says Cristina Chaplain, the GAO director who provides oversight for NASA, including the Commercial Crew program. SpaceX hopes to fly that test by this November, with Boeing targeting late 2019 or early 2020.