In a statement to Bloomberg, Facebook reiterates that it was "happy" with the test flight, which checked everything from basic aerodynamics to controls. There were "no major unexpected results," the social network says. It likely wasn't catastrophic, then, but the NTSB's involvement still raises eyebrows. Is it investigating just to be cautious, or is this more than a small snag?

Whatever the situation, it's only going to add to Facebook's headaches as it tries to offer free, far-reaching internet access. On top of the imperfect drone flight, it lost a satellite to SpaceX's Falcon 9 explosion on September 1st. Both ventures are inherently risky -- Aquila is effectively a barebones solar-powered wing -- but we suspect that Facebook wasn't expecting to run into that much trouble in a relatively short time.