Aviation accident numbers can vary greatly from year to year, but in three of the past five years for which data are available, Hawai'i had one of the worst accident rates in the nation, federal records show.

Hawai'i had the fourth highest civilian air accident rate nationally in 2005 and 2004, according to data from the National Transportation Safety Board and the Federal Aviation Administration. The combined data for general aviation, which includes private and small-scale commercial operations, and air taxi flights, including air tours, indicate the state recorded 12.4 air accidents per 100,000 flight hours in 2005 and 11 accidents per 100,000 hours the previous year.

Wyoming had the highest rate, at 15.6 accidents per 100,000 flight hours in 2005, followed by Alaska and Idaho. The same three states also had the worst air accidents rates in 2004.

Data for 2006 are not yet available.

Hawai'i did much better in 2002 and 2003, with accident rates that were among the lowest in the country. NTSB records show that in 2002, only three aviation accidents were reported, an unusually low number for the state. But the statistical aberration followed a year in which Hawai'i had the third highest accident rate in the country, with nine accidents involving general aviation and air taxi operations that resulted in an accident rate of 13.2 accidents per 100,000 flight hours.

The accidents included in the NTSB database cover everything from hot-air balloon mishaps and a weekend flier in a single-engine airplane clipping a runway sign with a wingtip to multiple-fatality airline crashes.

Experts caution that it's difficult to draw sweeping conclusions from the numbers because "general aviation" includes a variety of commercial and private flying operations using different types of aircraft and pilots of varying degrees of training and experience.

Air tours have come under increasing scrutiny with each fatal crash. From 1987 to 2006, airplane and helicopter tours accounted for 16 of 60 fatal crashes in the state.

Most of the air tour accidents occurred before the FAA instituted new safety rules in late 1994 that targeted air tour operations in Hawai'i.

Special Federal Aviation Regulation 71 requires tour flights that travel over the ocean to be equipped with floats to improve the chances of a safe emergency ditching, or to provide passengers with flotation gear. The rules also set a minimum altitude of 1,500 feet and mandate that pilots file a helicopter performance plan before each flight and that passengers be given a briefing on water-ditching procedures.

"The number of air tour accidents has plummeted since we implemented SFAR-71," said Ian Gregor of the FAA's Western-Pacific Region.

During the 12 years before the new regulation, from 1983 to 1994, there were 52 air tour accidents, including 12 fatal crashes that claimed 47 lives. In the 12 years after the rules took effect, from 1995 to 2006, there were 25 air tour accidents, with seven fatal crashes that killed 26.

So far in 2007, there have been two fatal helicopter tour crashes resulting in five deaths. Both occurred last month on Kaua'i and appear to have been triggered by mechanical problems, although a final determination by the NTSB is months away.

"The accident rate (for air tours) is not trending up, despite the two tragic events. There were no fatal crashes in 2006 and one each in 2005 and 2004," Gregor said.

He said that in seven of the past 12 years since SFAR-71 went into effect, there were no fatal air tour accidents in Hawai'i.

"One of the important results was intangible. It put everybody on notice that, 'Look, the FAA considers the number of accidents in the past to be unacceptable and we can work together to take steps to reduce it.' It focused everybody's attention on the issue," he said.

The rules have proven so effective that the FAA extended them to air tour operations across the country effective March 15.

The NTSB is seeking further regulation of the air tour industry, and in February issued additional safety recommendations in the wake of its investigation of two Kaua'i helicopter crashes in 2005 and 2004 that killed a total of eight people. Both fatal accidents were caused by pilots flying into adverse weather.

The recommendations include mandatory training in local weather patterns for newly hired air tour pilots and increased oversight and additional safety requirements for air tour companies that operate under the "Part 91" general aviation category. Part 91 air tour flights are restricted to a 25-mile radius and must take off and land at the same location, with no stops in between.

FATAL ACCIDENTS

The FAA said that approximately seven Hawai'i air tour companies fly as Part 91 operators, while 21 are doing business as Part 135 on-demand air taxi operators, which have fewer flight restrictions but more stringent flight rules and pilot qualifications.

Major air carriers had two fatal accidents in Hawai'i from 1987 to 2006, resulting in a total of 10 deaths, the NTSB data show. The first occurred April 28, 1988, when an Aloha Airlines interisland jet lost part of its upper cabin in midflight because of structural failure. A flight attendant was killed.

Nine passengers died Feb. 28, 1989, when a cargo door blew off a United Airlines jet that had taken off from Honolulu bound for Australia.

That same year, Hawai'i suffered its worst interisland air disaster, when 20 were killed on an Aloha IslandAir commuter flight that slammed into a Moloka'i cliffside when the pilot became lost in the clouds.

Hawai'i has its share of aviation hazards, including mountainous terrain, ocean expanses, quick-changing localized weather conditions, and skies that are becoming increasingly crowded because of the expansion of commuter air service, recreational flying and helicopter air tours, which launch hundreds of sightseeing flights daily.

Industry officials say these challenges have been offset to a degree by improved aircraft and avionics technology and stricter air tour safety rules that have helped reduce the number of aviation accidents in Hawai'i over the past 20 years.

NTSB data show an average of 12.1 accidents per year over the past 10 years, from 1997 to 2006, compared with 15 accidents per year over the preceding decade, from 1987 to 1996.

The average number of fatal accidents per year also dropped, from 3.4 to 2.6 when comparing the two decades, and air crash fatalities were down from an average of 12 per year to 7.3 per year. Declines were seen in both airplane and helicopter accidents, and accidents involving general aviation operations and air taxi flights, which include air tours.

ADVANCES IN SAFETY

Former airplane tour pilot Mac Smith, now chief flight instructor with Flight School Hawaii, said ongoing technological advances in avionics are improving air safety across the board. The FAA is in the process of implementing a National Automatic Dependent Surveillance-Broadcast program that will use Global Positioning Satellites instead of radar to help pilots and air traffic controllers more accurately track aircraft in the sky and on the runway.

Hawai'i is "a prime candidate" for the surveillance technology, the NTSB said in its February report, because of its limited air traffic control coverage and "high-density air traffic." The safety board wants the FAA to require Hawai'i air tour operators to equip their aircraft with the technology within one year of the installation of a functional national program, which could take 20 years.

The NTSB also noted the Islands' mountain winds and rapidly changing cloud conditions as potential flying hazards. Smith said blustery trade winds create turbulence "most of the time to some extent."

"In general, the Hawaiian Islands are a very nice place for flight training, but we do have our challenges," he said. "It's windier here than most spots on the Mainland and that has a big effect on landings and takeoffs ... And we have the additional burden of flying over water."

The state's mountainous terrain and small land area leave few flat, open spaces for emergency landings. "There are lots of open areas on the Mainland and thousands of airports, so you're always within gliding distance," said Smith, 53, who earned his pilot's license in 1974. "Here, we have to ditch in the water."

Training in water landings and ocean survival skills are required at Flight School Hawaii, which has between 50 to 60 active students, Smith said.

Reach Christie Wilson at cwilson@honoluluadvertiser.com.