The float plane carrying former Sen. Ted Stevens that crashed in Alaska this week was equipped with a distress beacon and a technology meant to alert the pilot that dangerous terrain was ahead, the chairwoman of the National Transportation Safety Board said Friday.

But no beacon was detected after the crash and it still wasn't clear whether the system meant to alert the pilot was on or was working just before the crash, chairwoman Deborah Hersman said at a news conference in Anchorage.

Monday's crash killed five people, including the 86-year-old Stevens — the longest-serving Republican senator in history and the patron saint of Alaska politics.

Four people survived, and investigators interviewed two of the survivors on Friday.

Hersman said one of the survivors described the crash by saying: "They were flying along, and they just stopped flying."

The same survivor said he didn't notice any changes in the plane's pitch or hear any unusual engine sounds right before the crash.

Hersman didn't identify the survivors who spoke with officials on Friday. She did not say why she wasn't naming the two who were interviewed.

Former NASA chief Sean O'Keefe, his son, Kevin O'Keefe, lobbyist Jim Morhard and lobbyist William "Willy" Phillips Jr. lived through the crash.

An Anchorage hospital on Friday upgraded Sean O'Keefe from critical to serious condition. Kevin O'Keefe remained in fair condition, Morhard also was in fair condition and Phillips was in good condition.

Hersman said one survivor recalled the group deciding during lunch at a southwest Alaska lodge to head to the fishing camp, a trip that had been put off in the morning due to poor weather.

The survivor said conditions had improved by the afternoon. He said he fell asleep about 10-15 minutes into the Monday afternoon flight and woke up after the crash, Hersman said.

Authorities have said that, had the most direct route been taken, the crash would have occurred about 15-20 minutes after takeoff, but it wasn't yet clear if that's the path that was taken.

Hersman said the pilot, Theron Smith, didn't request a weather briefing before departure. However, investigators have been told there was Internet service at the camp and he may have checked conditions that way.

Investigators have been examining the pilot's log book, weather information and the mechanics of the plane.


Associated Press Writers Rachel D'Oro, Mary Pemberton and Mark Thiessen in Anchorage, Alaska, and AP News Researcher Julie Reed Bell in Charlotte, N.C., contributed to this report.