DILLINGHAM, Alaska ? A pilot who spotted the wreckage of the amphibious plane carrying former Sen. Ted Stevens looked down on the gashed mountainside and thought that no one could’ve survived such a crash.

Then, he heard another pilot say on the radio: A hand was waving for help from a window of the red-and-white aircraft.

“It surprised me because I didn’t think it was survivable,” said Eric Shade, 48, owner of Shannon’s Air Taxi.

The discovery set in a motion a frantic rescue effort that culminated when National Guardsmen had the four dazed survivors, suffering from broken bones and other injuries, airlifted off the mountain. Five others, including the state’s most revered politician, were dead.

A fishing trip that Stevens and his friends have made for years to a southwest Alaska lodge — sometimes drawing criticism for hosting lobbyists and lawmakers there to discuss government issues — had ended in tragedy and left family searching for answers.

The cause of the crash was being investigated on Wednesday as National Transportation Safety Board officials hiked to the scene and began examining the wreckage, chairwoman Deborah Hersman said. They had hoped to interview the survivors Wednesday in the hospital but their medical conditions made it impossible.

Officials said a technology that Stevens had long pushed to improve air safety in Alaska wasn’t installed in the downed plane. It was unclear whether the instruments would’ve prevented the Monday crash.

Several medical volunteers who scrambled up the boulder-strewn slopes to the crash site found survivors trapped inside the fuselage, with one still strapped into the co-pilot seat. Rescuers had to cut alders to reach survivors, and then ripped open the plane to get them out.

“They didn’t do too much talking with us,” said Alaska Air National Guard Senior Master Sgt. Jonathan Davis, one of the rescuers lowered onto the mountain from a helicopter. “If they did talk, they were asking for pain medication, and we helped them with that.”

Stevens, 86, had close ties to everyone on the plane, including Anchorage-based General Communications Inc., a phone and Internet company that owned the aircraft, and the lodge where the passengers were staying.

“These were old friends who stayed in touch and loved him,” said Stevens’ friend, Russ Withers.

GCI frequently hosted high-profile guests, politicians and regulators at the Agulowak Lodge on Lake Aleknagik for fishing trips, drawing scrutiny from Alaska lawmakers over whether the expeditions violated ethics rules.

At a hearing in 2002, lawmakers grilled GCI executive Dana Tindall, who died in the crash, about the trips.

Tindall testified that Stevens and William “Bill” Phillips Sr., who also died in the wreck, once arranged for a staff member to travel to the lodge to learn about the telecommunications world as GCI looked to expand its business.

“We entertain business associates. We entertain — there have been FCC commissioners out there. And there have been members of the United States Congress out there,” Tindall told lawmakers.

Stevens and ex-NASA chief Sean O’Keefe, who was also on the plane and survived, were fishing companions and longtime Washington colleagues who worked together on the Senate Appropriations Committee led by the GOP lawmaker. Stevens became a mentor to him.