The first private spaceflight companies will carry humans to the International Space Station in 2017. Or at least that's what NASA is aiming for. The space agency has already placed orders with Boeing and SpaceX to be ready to carry human cargo by the end of next year.

That deadline might not be realistic, according to a new report from the Aerospace Safety Advisory Panel (ASAP), an organization that makes safety recommendations to NASA.

The report praised NASA's Commercial Crew Program, which funds private companies to develop the rocketry and vehicles needed to ferry astronauts to and from the space station.

However, the report says "there is a high likelihood of delays to the first test flights," and raises some concerns regarding the program's riskiness.