NASA is on track to bring human spaceflight back to the US. The agency has ordered its first "crew rotation" mission from Boeing, which will involve ferrying astronauts to the International Space Station (ISS). NASA says it expects to make a similar order with Elon Musk's SpaceX later this year -- afterwards, it will decide which of the two companies to green-light for the first mission in late 2017. However, this milestone moment in US spaceflight could easily shift. For one, Boeing and SpaceX still need to complete NASA's certification process before they can undertake any missions. For another, NASA's Commercial Crew Program is dependent on adequate funding through 2016 and beyond. If it comes up short, the agency says it "will have to delay future milestones for both partners proportionally and extend sole reliance on Russia." We're keeping our fingers crossed.