The float plane that crashed in southwest Alaska this week, killing former U.S. Sen. Ted Stevens and four others, was equipped with technology meant to alert the pilot if he was headed dangerously toward terrain.
But National Transporation Safety Board chairwoman Deborah Hersman said at a news conference Friday that it still isn't clear whether the system was on or working at the time of Monday's crash.
It wasn't the technology that Stevens himself had championed to help improve air safety in Alaska.
Investigators continued their search for answers Friday, including conducting interviews with two of the four survivors and working to bring the wreckage off the hillside for closer inspection.
The float plane crashed Monday en route from a lodge to a southwest Alaska fishing camp.
Camp guide Byron Orth said the lodge called guides to let them know the party was heading to the Nushagak River camp. But when no one showed up, Orth figured the trip had been canceled. Hours later, the lodge called and asked if the group was returning yet.
Orth, a Beaverton, Ore., resident who has spent the past six summers working at the fish camp, said people at the camp and lodge feared the worst had happened.
"You're hoping for the best, but there's a bad feeling in your stomach," he said.
Stevens' daughter said her father, a pilot in World War II, was an advocate of making planes safe.
"He loved flying ... he got certified to fly floatplanes just a few years ago," Lily Stevens Becker said Friday on the "TODAY" show. "He had no concerns about flying in Alaska, but he was concerned about making planes as safe as possible."
Hersman has said the plane lacked a technology Stevens had championed, technology intended to allow pilots to see cockpit displays, concise weather information and location of other aircraft in the area. But she said it had a "nicely equipped" cockpit and that investigators were still trying to get a sense for all the equipment on board.