Investigators face number of challenges in recovering, analyzing Horizon flight wreckage
But crews are facing a number of challenges in their recovery of the aircraft wreckage.
Tuesday, crews uncovered a big piece of the plane's tail section, but KOMO News has learned it will take a few more days to remove all the debris, due to the terrain, trees and water.
"The island is like two and half miles down," says year-round island resident Jerry Tomlin. "Way down at the south end there is nothing there, not even a road."
Watch: Air 4 is over the crash scene on Ketron Island as crews work to salvage the wreckage:
Salvage teams are up against snapped trees, strewn debris, and terrain dense with trees and brush. The NTSB said heavy equipment had to be brought in to remove downed trees on top of debris.
Crews began their work over the weekend by cutting a roadway, and two more truck loads hauled debris off the Tuesday.
But now the NTSB says the pieces are getting smaller -- all of it the work of a salvage company, collecting and tagging every piece for the FBI to review in its investigation.
NTSB regional chief Debra Eckrote said the trees were so dense that and the impact essentially shredded the plane, initially stripping its wing sections and with the heaviest pieces, the landing gear strut, and the engine at the opposite end of a debris field a couple hundred feet long.
And crews are also at the mercy of the tide. Every piece of equipment and collected debris relies on a ferry or barge.
Eckrote says the NTSB considers the crash an intentional act, not an accident, which is why their job is now done, unless the FBI asks for more assistance in their search for answers.
The NTSB will continue to assist the FBI in analyzing the black boxes -- a flight data recorder and the cockpit voice recorder. The NTSB's lab at its headquarters in Washington, D.C. will work on extracting the information on both of the black boxes.
The NTSB says the cockpit voice recorder has some damage, but they don't yet know the extent of it.