Evidence shows the Care Flight plane that crashed Friday night killing everyone aboard broke up in flight.
NTSB officials will be on the scene near Stagecoach, NV for days.
"How do we know if the airplane broke up in flight? We found parts of the airplane one-half to three-quarters of a mile away" from the crash scene, NTSB Vice Chair Bruce Landsberg told reporters at a briefing. "Right now, we just don't know. This is like a three-dimensional puzzle. It's harder when you don't have the pieces all in one place."
The pilot of the single-engine Pilatus PC-12 was notified about turbulence in the area around Reno. Audio recordings revealed the air traffic controller issuing the warning and moments later, trying to reach him again.
Airline pilots also tried to communicate with the plane and were asked to keep an eye out for wreckage.
It took local firefighters more than two hours to find the downed aircraft.
Scott Walton was a PC-12 pilot and spent many years flying and teaching students around the world. He left behind a wife and three small children.
The others aboard the Flight Care plane included Flight Medic Ryan Wilson, a new father; Flight Nurse Ed Prikola, a father with two young children; Mark Rand, the patient, and his wife, Terry.
Fire and rescue personnel along with law enforcement officers from the Stagecoach and Reno areas escorted the crew.