Representatives from the three different companies chosen by NASA to develop private space taxis to carry astronauts to orbit say their vehicles are making substantial progress toward launching people into orbit within the next few years.

The companies — Space Exploration Technologies Corp. (SpaceX), The Boeing Company, and Sierra Nevada Corp. — are competing to fill the gap left by NASA's retired space shuttles for the launching of cargo and crews to the International Space Station. Each private space taxi firm has received funding from NASA under the Commercial Crew integrated Capability program (CCiCap) to complete a series of development milestones with the goal of taking over transportation to low-Earth orbit from the Russians.