NASA Administrator Michael Griffin told an industry group Thursday that NASA has looked into what it would take to keep flying the aging shuttle past 2010. President George W. Bush wants to replace the shuttle with a new spaceship to go to the moon. But that would mean five years of relying on Russia to get astronauts to the international space station.
President-elect Barack Obama has proposed delaying the shuttle's retirement.
Griffin said flying shuttles until a replacement is ready in 2015 would cost $15 billion over five years.