"It would mean the cost of Sea-Tac operations and expansion would be spread among the remaining airlines," Dinsmore said in a statement. "That would translate into higher ticket prices for air passengers not flying on Southwest."
Port officials argue that they can work with Southwest to bring its airport costs under control, even with the expansion.
Alaska Airlines, the largest carrier at Sea-Tac, has voiced its opposition. Alaska, which along with its affiliate Horizon Airlines accounts for about 48 percent of that airport's traffic, said that it could move as many as 100 daily flights to Boeing.
That could cut even further into Sea-Tac's revenues, forcing fees to skyrocket as the new facilities come on line.
"We are opposed to any major carrier exiting Sea-Tac," Alaska spokeswoman Amanda Tobin said. "We would have to consider moving flights for purely competitive reasons."
The situation has some remarkable similarities to the debate in North Texas over the Wright Amendment. Here, Southwest has refused to fly from D/FW Airport because, the airline claims, the airport is too congested and the costs are too high.
Southwest also cites American Airlines' formidable D/FW hub, one of the largest in the nation. American fiercely defends its turf at D/FW, and Southwest executives say they don't typically operate at so-called "fortress hubs."
And Love, close to downtown Dallas, is more convenient to the largest population center, much like Boeing Field in Seattle.
That's why the airline is seeking to repeal the amendment, which restricts flights from Love to the states adjacent to Texas, as well as Kansas, Mississippi and Alabama, rather than move to D/FW.
Southwest would like to expand its Love service to add about 50 flights, serving popular cities like Chicago, Los Angeles and Las Vegas.
Like Sea-Tac, D/FW officials worry that having an unrestricted, smaller, cheaper competing airport could do serious damage. A study commissioned by D/FW concluded that the airport could lose 21 million passengers, a 35 percent drop, if the amendment is lifted.
And American Airlines' response has mirrored Alaska's. Fort Worth-based American has declared that it will move a substantial number of flights -- perhaps hundreds -- to Love Field if the restrictions are eliminated.
Neighborhood groups in both cities have mobilized, airing fears that expanding the smaller airports could mean more traffic and noise for nearby residents.
There are, of course, many fundamental differences in the two cases. Boeing Field isn't restricted by federal law. Southwest doesn't want to switch airports here, just expand its current home. And although costs are rising at D/FW, they remain far below the levels at Sea-Tac.
Ricks said the Seattle debate, so far, has lacked the bitterness of the North Texas brawl.
"There isn't the rancor we've had here, with this ancient rivalry between two different jurisdictions," he said. "Seattle doesn't have that historical baggage that Dallas and Fort Worth have."
Ultimately, both debates have the same roots -- Southwest's need to bring in more money and cut more expenses if it wants to continue as the nation's largest profitable airline.
"Southwest needs to go where it can collect the most people at the best price, and that doesn't necessarily mean the big airport in town," said Boyd, the airline consultant.
Ray Neidl, an airline analyst with Calyon Securities in New York, said Southwest doesn't have much choice if fuel prices remain high.
Southwest "may offset higher fuel costs with revenue offsets and trimming nonfuel costs further," he said in a recent investment report. He added that he believes that Southwest will be one of only two profitable airlines this year.
Southwest's Ricks stresses that although the drive to repeal the Wright Amendment is moving at full speed, the Seattle proposal is in its infancy. He said any move will probably take four to five years at least.
He also doubts that it will ever become as passionate as the Wright Amendment debate.
"All of these things that tend to be controversial in Dallas and Fort Worth, that doesn't seem to be the case in the Puget Sound area," he said. "Things have been a lot more relaxed there."
American Airlines executives say they might move their Seattle operation to Boeing Field if rival Southwest Airlines opens that airport to commercial service.
Seattle-based Alaska Airlines sent a proposal to the King County Executive's Office late Friday outlining plans to offer 68 flights a day and to build a $150 million terminal with eight gates.
Two airline titans are stirring up an old squabble on Capitol Hill, with lower airfares and more service between Kansas City and Dallas among the potential stakes.