Heavy traffic at the International Space Station (ISS) has pushed SpaceX's next crewed launch to the orbiting lab for NASA back a week.

In photos: SpaceX's Crew-2 mission to the International Space Station.

Crew-3 will launch NASA astronauts Raja Chari, Tom Marshburn and Kayla Barron and European Space Agency (ESA) astronaut Matthias Maurer to the orbiting lab in a Crew Dragon capsule.

The foursome will leave Earth atop a SpaceX Falcon 9 rocket from Launch Complex 39A at NASA's Kennedy Space Center in Florida for what is expected to be a six-month mission, a typical space station tour of duty.

SpaceX's Crew-2 mission, which arrived at the ISS on April 24, will depart "early to mid-November" after Crew-3's arrival, NASA officials said.

The next crew exchange after Crew-3's will happen "no earlier than mid-April 2022," NASA officials said in the statement, "with the partner spacecraft and launch vehicle to be determined at a later date." This could mean a flight by a Russian Soyuz spacecraft or an American commercial crew vehicle. .

For nearly nine years afterward, the agency relied solely on Soyuz spacecraft for crew transportation.

In the meantime, the agency worked on developing a commercial crew program, awarding $6.8 billion in 2014 to SpaceX and Boeing for future astronaut launches!