No definitive cause can be determined for the plane crash that killed former US Sen. Ted Stevens and four others last summer in Alaska, the National Transportation Safety Board said today. The board agreed at a hearing in Washington that "temporary unresponsiveness" of the pilot could be to blame, but the reasons can't be determined. There was no flight data or cockpit voice recorders on board—on a plane officials described as otherwise outfitted with state-of-the-art equipment. The front-seat passenger, one of the teenage passengers who survived, was said to be asleep at the time of the crash.
It's rare for so many people to work so long on an investigation without an agreed upon conclusion, according to a NTSB chairwoman. With a myriad of potential theories—the pilot's history of strokes and the recent death of his son-in-law, lack of functioning onboard technology, poor weather, and no sign of mechanical trouble—there was limited factual data to work from, leaving investigators without significant evidence to support any single theory, the chairwoman said. (Read more Ted Stevens stories.)