Boeing and SpaceX winners in NASA Commercial Crew round
The Commercial Crew program is aimed at ending the reliance on Russia to provide the transportation.
Based on each company's tender, Boeing will receive $4.2 billion and SpaceX $2.6 billion.
The third contender, and the most radical design, Sierra Nevada Corporation's Dream Chaser craft was knocked out of the round.
The certification process will involve a flight with at least one NASA astronaut aboard to verify the fully integrated rocket and spacecraft system can launch, manoeuvre in orbit, and dock to the space station, as well as validate all its systems perform as expected.
Once each company passes NASA certification, they will conduct at least two, and as many as six, crewed missions to the space station.