Investigation is on after a charter plane crash killed 8The Cessna 441 was attempting a second landing in rapidly worsening fog when it crashed about one-third of a mile from a remote military runway in western Alaska, killing all eight people aboard, authorities said Friday.The pilots could not see the gravel airstrip and were relying entirely on instruments as they approached the Cape Newenham Long Range Radar Site, National Transportation Safety Board Alaska region chief Clint Johnson said. Their first landing attempt had to be aborted because visibility was too poor, as required under aviation regulations.The crew then made a second approach, but the aircraft crashed before reaching the runway. Its final flight path was captured by radar at the site before the plane lost contact, Johnson said. Search teams later found the aircraft's fragmented wreckage.Weather conditions had deteriorated sharply around the time of the crash. An automated weather observation system near the airstrip reported fog, low clouds and visibility of about 10 miles in the minutes before the accident. About 15 minutes after the crash, visibility had fallen to less than one-quarter mile, according to the National Weather Service.The airstrip's location added to the challenge. The runway is surrounded by mountainous terrain on three sides, and the Federal Aviation Administration recommends pilots use GPS and other instruments when landing there.The crash raises questions about the decision to attempt a second approach as conditions deteriorated, though investigators have not determined what caused the aircraft to go down. NTSB investigators were traveling to the remote site Friday to begin examining the wreckage and circumstances surrounding the crash.The aircraft was operated by Anchorage-based Security Aviation. On board were the two pilots, two US Army Corps of Engineers employees and four contractors. The military has not disclosed what work they were carrying out at the radar site.The Cape Newenham site, about 450 miles west of Anchorage, was built in the 1950s as part of a network designed to provide early warning of a Soviet missile attack. It closed as an active outpost in 1983 but is still visited by civilian contractors who maintain its radar system.