NASA commercial crew astronauts Victor Glover and Michael Hopkins climb after takeoff in their T38 aircraft during a training flight in Houston, Texas, U.S. May 21, 2019.

NASA commercial crew astronauts Michael Hopkins and Victor Glover run through a training session at a replica International Space Station (ISS) at the Johnson Space Center in Houston, Texas, U.S., May 22, 2019.

A view inside a replica science lab of the International Space Station at Johnson Space Center in Houston, Texas, U.S., May 22, 2019.

NASA commercial crew astronauts Victor Glover and Michael Hopkins taxi their T38 aircraft for a training flight in Houston, Texas, U.S., May 21, 2019.

NASA commercial crew astronauts Michael Hopkins and Victor Glover run through a training session at a replica International Space Station (ISS) at the Johnson Space Center in Houston, Texas, U.S., May 22, 2019.

NASA commercial crew astronauts Michael Hopkins and Victor Glover run through a training session at a replica International Space Station (ISS) at the Johnson Space Center in Houston, Texas, U.S., May 22, 2019.

NASA commercial crew astronauts Michael Hopkins and Victor Glover run through a training session at a replica International Space Station (ISS) at the Johnson Space Center in Houston, Texas, U.S., May 22, 2019.

NASA commercial crew astronauts Michael Hopkins and Victor Glover run through a training session at a replica International Space Station (ISS) at the Johnson Space Center in Houston, Texas, U.S., May 22, 2019. Picture taken May 22, 2019. REUTERS/Mike Blake6 - RC1635431030

The crew notebook of NASA commercial crew astronaut Victor Glover is shown as he trains inside a replica International Space Station at the the Johnson Space Center in Houston, Texas, U.S., May 22, 2019.

The sleeve of NASA commercial crew astronaut Victor Glover reflects the SpaceX spacecraft he will be riding in when lifts-off to the International Space Station on a future mission as he trains at the the Johnson Space Center in Houston, Texas, U.S., May 22, 2019. Picture taken May 22, 2019. REUTERS/Mike Blake - RC128040A7D0

NASA commercial crew astronaut Michael Hopkins works through an emergency procedure inside a replica International Space Station (ISS) at the Johnson Space Center in Houston, Texas, U.S., May 22, 2019.

The crew notebook of NASA commercial crew astronaut Victor Glover is shown as he trains inside a replica International Space Station at the the Johnson Space Center in Houston, Texas, U.S., May 22, 2019.

Video screens monitor the inside of a replica International Space Station at Johnson Space Center in Houston, Texas, U.S., May 22, 2019.

A pair of Vans NASA sneakers are worn by commercial crew astronaut Victor Glover as he trains inside a replica International Space Station at the the Johnson Space Center in Houston, Texas, U.S., May 22, 2019.

NASA commercial crew astronauts Michael Hopkins and Victor Glover run through a training session at a replica International Space Station (ISS) at the Johnson Space Center in Houston, Texas, U.S., May 22, 2019. Image for illustrative purposes.

NASA commercial crew astronauts Michael Hopkins and Victor Glover run through a training session at a replica International Space Station (ISS) at the Johnson Space Center in Houston, Texas, U.S., May 22, 2019.

A view showing a life-size replica of the International Space Station at Johnson Space Center in Houston, Texas, U.S., May 22, 2019.

The sleeve of NASA commercial crew astronaut Victor Glover reflects the SpaceX spacecraft he will be riding in when lifts-off to the International Space Station on a future mission as he trains at the the Johnson Space Center in Houston, Texas, U.S., May 22, 2019.

NASA commercial crew astronauts Victor Glover and Michael Hopkins walk out to their aircraft prior to a training flight in Houston, Texas, U.S., May 21, 2019.

NASA commercial crew astronauts Victor Glover and Michael Hopkins talk over their flight procedures prior to a training flight in Houston, Texas, U.S., May 21, 2019.

NASA astronaut flight gear is shown in a pre-flight ready room in Houston Texas, U.S., May 21, 2019.

NASA commercial crew astronauts Victor Glover and Michael Hopkins walk out to their aircraft prior to a training flight in Houston, Texas, U.S., May 21, 2019.

NASA commercial crew astronauts Michael Hopkins and Victor Glover run through a training session at a replica International Space Station (ISS) at the Johnson Space Center in Houston, Texas, U.S., May 22, 2019.

NASA commercial crew astronauts Michael Hopkins and Victor Glover run through a training session at a replica International Space Station (ISS) at the Johnson Space Center in Houston, Texas, U.S., May 22, 2019.

NASA commercial crew astronauts Michael Hopkins and Victor Glover run through a training session at a replica International Space Station (ISS) at the Johnson Space Center in Houston, Texas, U.S., May 22, 2019.

NASA commercial crew astronauts Victor Glover, Michael Hopkins, Bob Behnken and Douglas Hurley gather for a group photo at Johnson Space Center in Houston, Texas, U.S., May 21, 2019.