While some West Seattle residents worry about the noise of potential Southwest Airlines passenger jets flying along two sides of West Seattle, the airline CEO said water would reduce the noice from its planes.

Gary Kelly, chief executive officer of Southwest Airlines, told the King County Council if his airline is allowed to move from Sea-Tac International Airport to Boeing Field, up to 95 percent of Southwest departures and landings would be over Elliott Bay. Flying over water would reduce the impact of jet noise on most Seattle neighborhoods.

Flights would depart Boeing Field northward above the Duwamish corridor and then turn west above Elliott Bay. Conversely, arriving flights would come in over the bay and then drop southward to land at Boeing Field.

Boeing Field, also known as King County International Airport, is owned by the county, so the County Council has to approve Southwest Airlines' move to Boeing Field.

Boeing Field lies due east of West Seattle. The runway stretches approximately from Morgan Street at the north end to Roxbury Street at the south end.

Southwest Airlines currently has 38 daily flights in and out of Sea-Tac Airport. The airline plans 85 flights per day, with more trips to Southern California, if allowed to move to Boeing Field, Kelly said.

The increased noise of those flights brought numerous sign-waving protestors to the Sept. 12 meeting at the Museum of Flight at Boeing Field.

"Noise is the elephant in the room," said County Council President Larry Phillips.

Among those opposing the move was Mayor Steve Mullet of Tukwila. He predicted the move would reduce property values on homes affected in his community by about 30 percent.

Southwest Airlines, which flies Boeing planes exclusively, wants to use the Boeing 737-700 partly because it's quieter than other jet airliners.

The plane has "blended winglets," a wingtip design that gives the plane greater lift and enables it to climb steeper with less energy, which means the engines work less and are quieter, said Sandy Angers of Boeing.

The 737-700 also is equipped with global positioning satellite instruments to hone closely to a prescribed route over Elliott Bay.

The 700 series us much quieter, Angers said. Its "noise footprint," the area on the ground below the plane where its engines can be heard, is one-tenth the size of the 737-200, its predecessor, she said.

Another Southwest Airlines' promise is no "red eye" flights from midnight to 5 a.m.

The airline does not yet know how many decibels of noise its planes would produce operating out of Boeing Field but promised to pay for a sound study to find out. The results will be published in the proposal's environmental impact statement, Kelly said.

Southwest Airlines offered to spend $130 million to build a new terminal with eight gates. The building would spread more than 120,000 square feet.

Southwest also would build a six-level parking facility with nearly 3,300 parking spaces, said Marilee McInnis, a Southwest Airlines spokeswoman. Two ground-level parking lots would have about 700 additional spaces.

County Councilman Dow Constantine, who represents West Seattle, Burien and Vashon Island, is opposed to the move.

"I have long opposed expansion of Sea-Tac Airport and the third runway," he said. "I'm similarly concerned about the effect (of Southwest Airlines proposed move to Boeing Field) on urban neighborhoods that already struggle with many tough issues.

"Let's not rush into this because of a single airline's wishes," Constantine said.

Among the tenants already at Boeing Field is San Juan Airlines, which flies to the San Juan Islands. Cargo carriers such as Airborne Express and United Parcel Service operate facilities there. Airlift Northwest helicopters equipped for medical emergencies are based there along helicopters from the King County Sheriff's Office and Washington State Air National Guard. Boeing Field also is home to numerous corporate jets, aircraft owned by the general public, and there are flight schools based there too.

There were 300,000 takeoffs and landings at Boeing Field last year, although some were touch landings that are part of flight training.

Sea-Tac International Airport had 360,000 takeoffs and landings last year.

Southwest Airlines pays the Port of Seattle for space it uses in the Sea-Tac terminal. It also pays landing fees. According to Kelly, Sea-Tac Airport is the most expensive of the 60 U.S. airports where the airline operates.

Southwest Airlines agreed to share costs to build the third runway at Sea-Tac but the company had "concerns about the cost," Kelly said. Southwest signed onto the third runway project when it was estimated to cost $400 million. But cost estimates for the third runway have risen to $1.1 billion, and that's something the company never agreed to, Kelly told the County Council.

Of concern to the council are the new roads and other public facilities that King County would have to provide at Boeing Field to accommodate a new airline, passenger terminal and parking facility.

The other consideration for the County Council is the economic loss for Sea-Tac Airport if one of its main tenants leaves, said Council President Phillips.

Phillips said the No. 1 issue on citizens' minds this year is whether Southwest Airlines should move to Boeing Field.

Like most other airports, King County receives grant money from the Federal Aviation Administration to help keep Boeing Field in operation, said Mike Alwine, a council legislative assistant. Among the stipulations for getting the money is that the airport must allow all types of aviation, including commercial, to use the airport, Alwine said.

The Federal Aviation Administration must give its blessing to Southwest's move to Boeing Field too. The federal agency can turn down the request if it thinks safety would be compromised or if there isn't enough space at Boeing Field to accommodate Southwest Airlines.

Southwest won't leave Sea-Tac Airport if its request to move is denied, Kelly said.

"But 38 flights a day is not sufficient for this market," he said.

However, Robert Bismuth of the Magnolia Community Club offered this advice to Southwest Airlines.

"Don't try to leverage a public asset against another public asset," he said.

Tim St. Clair can be contacted at tstclair@robinsonnews.com or 932-0300.