No clear answers for cause of 2018 Alaska sightseeing crash in Denali

Federal investigators couldn't determine whya sightseeing plane crashed in Denali National Park and Preservelast year, killing all five people on board, because they couldn'taccess the crash site.

The plane went down on a steep, hanging glacier at over 3,048 metresin elevation. The glacier calved last winter,burying the plane in up to 5,443 metric tonnes of ice,Anchorage TV station KTUU reported.

The National Transportation Safety Board, in its final report onthe August 2018 crash, lists the probable cause as"impact withterrain for reasons that could not be determined because theairplane was not recovered due to the inaccessible nature of theaccident site."

Typically, toxicology reports are conducted on pilots andmechanical assessments are done on the wreckage, but that wasn'tpossible in this case.

Forty-eight minutes into the plane's flight, the Alaska RescueCoordination Center received an alert from its emergency locator.Moments later, personnel from the plane's operator, K2 Aviation,received a call from the pilot reporting the plane had "run intothe side of a mountain."

Poor weather conditions hampered initial efforts to locate theplane. An eventual assessment of the scene indicated a wing had hitthe snow while the airplane was flying in what was likely reducedvisibility, the report states.

The National Transportation Safety Board said the aviationcompany did not use a formal risk assessment process, insteadrelying on conversations between pilots and the flight follower inTalkeetna or Anchorage.

"This could lead to an oversight of actual risk associated witha particular flight route and weather conditions," the reportstates.

K2 Aviation's base chief pilot said routes for glacier tourflights were subject to change at the pilot's discretion based on the weather at the time of the flight to provide the best tour experience, according to the report.

That individual alsostatedthat pilots were expected to report to base operations when changinga planned route, but this was not a requirement in the company'sgeneral operations manual, the report states.

The company's operators were out of country Wednesday andunavailable for comment, KTUU reported.