Pilot error was the probable cause of two tour helicopter crashes that occurred on Kaua'i on Sept. 24, 2004, and Sept. 23, 2005, killing a total of eight people, according to the National Transportation Safety Board.

In both cases, the board's final report released this week faulted pilots for continuing to fly in adverse weather.

In the 2004 case, a Bell 206B helicopter registered to and operated by Bali Hai Helicopter Tours Inc., crashed in mountainous terrain in Kalaheo, Kaua'i. The commercial pilot and the four passengers were killed. The board found that the pilot's decision to continue flight in turbulent, reduced visibility weather conditions apparently resulted in the pilot's spatial disorientation and loss of control of the helicopter.

Also contributing to this accident, according to the report, was the pilot's inexperience in assessing local weather conditions, inadequate Federal Aviation Administration surveillance of operating restrictions and the operator's pilot-scheduling practices.

In the 2005 case, an Aerospatial helicopter, registered to Jan Leasing LLC, and operated by Heli-USA Airways Inc. of Las Vegas crashed into the ocean — several hundred feet off the coast of Kailiu Point, near Ha'ena — during adverse weather conditions. Three tour passengers were killed, and the commercial pilot and two other passengers suffered minor injuries.

The board found the pilot's decision to continue flight into adverse weather apparently resulted in a loss of control due to an encounter with a microburst air current. Contributing to the accident's fatalities, the report stated, was the lack of helicopter flotation equipment.