A possible deal in which King County would essentially trade Boeing Field to the Port of Seattle for a rail corridor from Snohomish to Renton is not expected to have any effect on operations at Paine Field, an official said.

King County Executive Ron Sims and Port of Seattle CEO Mic Dinsmore on Wednesday announced the possible deal, in which the port would acquire the 47-mile rail line from Burlington Northern Santa Fe Railway – including a chunk in Snohomish County – and then trade it for county-operated Boeing Field.

King County would develop a recreational path on the railroad right-of-way. The Port of Seattle, which already owns and operates Sea-Tac Airport, would own Boeing Field as well.

“We’re not predicting any change or impact to Paine Field,” said Peter Camp, an executive director for Snohomish County. The county owns and operates Paine Field.

Last year, Southwest Airlines offered to build a $130 million terminal at Boeing Field to escape rising landing fees at Sea-Tac. The deal was quashed by Sims when Alaska Airlines also expressed interest in Boeing Field, and Sims said road improvements and other costs would be too rich for King County’s blood.

Dinsmore said Wednesday the port has no plans to add passenger flights to Boeing Field, though he said once Sea-Tac reaches its capacity, this could change.

Sea-Tac is projected to reach its capacity of 45 million passengers per year in 2021.

If the port were to add passenger traffic to Boeing Field and fees are raised again, would an airline seek relief by coming north?

No, said Greg Hauth, president of Save Our Communities, the Mukilteo-based group fighting any expansion of operations at Paine Field.

“What infrastructure do we have at Paine Field, in terms of parking, a terminal or security?” Hauth said.

Camp agreed.

“I don’t think that would push Southwest up here because the economics would be pretty stout,” he said. “Southwest hasn’t called us yet.”

A spokeswoman for Dallas-based Southwest Airlines said it’s too early to tell.

“Costs are very important to Southwest, and we’re working with (Sea-Tac) airport to keep those down,” spokeswoman Whitney Eichinger said.

Reporter Bill Sheets: 425-339-3439 or sheets@heraldnet.com.