BART's $386 million plan to extend light rail service to the Oakland International Airport has hit a dead end because it failed to attract private partners needed to help pay the cost.

A sagging economy and declining airline ridership dried up private sector interest in joining BART to build the 3.2-mile elevated tramway to whisk passengers between the Oakland Coliseum station and the airport.

BART was talking to three private consortiums in the past eight months. Two teams dropped out earlier this year, and the last one — which included Merrill Lynch & Co. for financing and Bombardier Transportation as a light rail car maker — dropped out recently, BART officials said this week.

"The economy had a big effect," said Gail Murray of Walnut Creek, the BART board president. "We needed a partnership to make this work. But it just didn't pencil out for them."

Murray and other BART officials said they have not given up on the idea of forging some new transit link to the airport, but they are going back to the drawing board to consider less expensive alternatives. "It's back to square one," BART spokesman Linton Johnson said.

BART, airport and regional transit agency leaders for years touted the airport connector as a way to make travel to the airport more convenient, and to reduce traffic congestion and air pollution in the region.

For $3, airport passengers now can ride AirBART shuttle buses between the Coliseum station and the airport. In 2007, the shuttle buses carried about 1.3 million riders, about 9 percent of the Oakland airport passengers, according to a BART report.

But travel time on the AirBART shuttle can vary from 12 to 60 minutes a trip, depending on traffic congestion, according to a BART report. Bus shuttle riders also must haul their suitcases through the BART faregates and down to buses at street level.

A tram, also called a people-mover system, would allow passengers to roll suitcases from BART trains to tram cars located on the same level.

BART had lined up $256 million for the tramway, including $109 million in Bay Area bridge toll money from the Metropolitan Transportation Commission; $98 million from the Alameda County Transportation Improvement Agency; and $42 million from the Port of Oakland, the landlord for the airport.

The Federal Transit Administration also pledged $25 million to help a project that would be one of the first public transit projects in the nation to be built as a public-private partnership.

Even will all the public funds, BART remained about $130 million short. To make up the difference, BART advertised for prospective private partners to build and operate the tramway after signing a 35-year concessionaire agreement.

Sharing of fare revenues would be worked out in the agreement.

Tom Radulovich, a BART board member from San Francisco, said that his agency should look again at dedicated bus lanes to the airport. "We said no to bus rapid transit before because Oakland didn't want to give up the road capacity, but I think it should back on the table," he said.

Radulovich said that BART officials learned to be cautious about new rail extensions because fares from the San Francisco airport failed to cover operating costs, as BART had predicted. "We have learned we cannot have rail extensions at any cost."

Reach Denis Cuff at 925-943-8267 or dcuff@bayareanewsgroup.com.