Honolulu International Airport has grounded its fleet of electric Wiki Wiki shuttle buses, citing maintenance and reliability problems, officials said.

The buses, which transport thousands of passengers each day between terminals and from arrival gates to the baggage claim area, have been temporarily replaced with older open-air diesel buses and trams.

Six air-conditioned vehicles were taken out of service in September, said Scott Ishikawa, Department of Transportation spokesman. In addition, airport officials have notified the contractor, GEM of Hawai'i, that four other buses scheduled to go into operation next year will not be accepted until the problems are resolved.

"We're disappointed that this action was necessary, since the air-conditioned vehicles were popular with the traveling public," Ishikawa said. "But until the contractor can demonstrate an acceptable level of reliability for the vehicles, they will remain grounded."

The six buses were put into service in late 2003 as part of a $2.5 million contract to improve airport passenger services.

Ishikawa said the problems never posed a safety threat to the public, but he would not identify the specific maintenance issues in the dispute because "the state will be discussing the matter with the manufacturer this month."

The grounded fleet includes four 25-passenger vehicles, which take passengers between terminal buildings, and two 100-passenger trams that bring arriving passengers from outlying gates to the baggage claim area. All of the vehicles remain under warranty, Ishikawa said.

They were built by Electric Vehicles International, a California-based company. Each bus has an all-electric power train and a propane gas engine that runs the air conditioning, Ishikawa said.

Top company officials plan to fly to Hawai'i this month to address the problem and suggest solutions, Ishikawa said. The company sent mechanics last month to work on the vehicles.

"We plan to test-run two of the repaired buses for reliability very soon," Ishikawa said.

A spokesman for GEM of Hawai'i would not comment. A spokesman for Electric Vehicles International could not be reached for comment.

It's the not the first time the company, which was founded in 1991, has had problems with its electric vehicles.

In 1999, city officials in Evansville, Ind., said three electric trolleys costing almost $600,000 would be returned to the company. It was a "never-ending problem trying to get the bugs out of the trolleys," the director of the Metropolitan Evanston Transit System said then, according to an Associated Press report.

A major problem with those trolleys was a charging system that didn't work properly. The problems required city workers to charge the trolley batteries every hour, rather than every four hours as the company said was needed.

The Hawai'i shuttle buses were part of a brief controversy even before they arrived in the Islands.

In 2002, another company, Enova, partnered with the state's Hawai'i Electric Vehicle Development Program and spent almost $1 million to develop an all-electric bus service at the Hono-lulu airport. But when delivery of a prototype of that bus was delayed by manufacturing problems, the state chose to move forward on the contract with GEM. The Enova bus still sits idle in a Kaka'ako parking lot.

The state also spent more than $12 million in 2002 to repair and upgrade ramps and roadways used by the Wiki Wiki buses. Those repairs included removing and replacing the concrete road surfaces used by the buses inside the secured portions of the airport.

Last year, the city of Anderson, Ind., where Electric Vehicles International was originally located, sued the company over an unrepaid $1.1 million loan it made to the company in return for the promise of creating 300 jobs in the city. The company has since relocated its manufacturing operations. In July, the company's president and investors agreed to a $500,000 settlement of the lawsuit, but city officials said Electric Vehicles International missed the first deadline to make a payment under the settlement.

Reach Mike Leidemann at mleidemann@honoluluadvertiser.com.