EVERETT — An investment firm’s bid to build a passenger-jet terminal at Snohomish County’s Paine Field would have to overcome a political split to get off the ground.

Propeller Investments needs the County Council’s approval to move forward with any deal, like the two-gate passenger terminal the company pitched last week. Until talks evolve further, it’s unclear what the proposed project would even look like.

Four of five council members are divided evenly over allowing commercial passenger flights at the county-run airport. A fifth says he’s undecided.

“It sounds like it’ll be coming to a head in six to nine months,” said Councilman Brian Sullivan of Mukilteo, a staunch opponent.

The potential tie-breaker is Terry Ryan of Mill Creek, a pro-business Democrat with a background in commercial real estate.

A few months is a relatively short amount of time to wait for what could be the final bout in a decades-long fight. Events have intensified of late.

New York-based Propeller Investments entered the picture Monday when it asked county airport officials to discuss a plan to lease ground space to build and operate a two-gate terminal. A meeting has yet to be scheduled, both sides said Friday. The company has met informally with several county leaders.

At Paine Field, Propeller envisions four or five commercial flights a day to regional destinations.

That fits within the number of flights the FAA studied for its 2012 environmental assessment. The study concluded that noise, traffic and pollution from commercial jets would not harm nearby communities. As is, Paine Field handles about 300 daily flights for general aviation and aerospace manufacturing. The airport is running at about a third of its capacity.

“It’s negligible,” Propeller CEO Brett Smith said of the effect his company’s plans would have.

The cities of Mukilteo and Edmonds, along with the Save Our Communities opposition group, challenged the adequacy of the FAA study during a hearing Wednesday before the U.S. 9th Circuit Court of Appeals. A ruling from a three-judge panel could take months.

There’s no legal reason Propeller would have to wait for the judges’ decision to advance its plans at Paine Field.

There may be practical reasons, however, said County Council Chairman Dave Somers, who supports commercial flights. An FAA ruling in the opponents’ favor could trigger extensive analysis.

“I would think it would delay it a year or more,” Somers said.

The FAA study was based on about 160 flights per week. That’s the combined total that Allegiant Air of Las Vegas and Alaska Airlines of Seattle had been proposing. Since then, Alaska has lost interest in establishing service at Paine Field, while Allegiant has been coy about its intentions.

Propeller isn’t saying which carriers it has in mind. Smith said Allegiant is not a financial backer.

The county is obligated to negotiate in good faith when someone wants to lease vacant airport property for aviation, according to the FAA.

The county might be able to assert more control over the issue by building and operating its own terminal. In fact, the county drafted blueprints for such a building last year. With two gates, the projected cost is $9.7 million.

Prior to that design work, the county had estimated a terminal would cost about $3 million — the figure that over the years has surfaced most often in the debate.

It’s not clear whether Propeller would pursue a similar design. Nor has anyone established who would own Propeller’s proposed building — the county or the company.

“Until we sit down and start talking, we won’t know,” Smith said.

Though Sullivan opposes commercial flights at Paine Field, he’d prefer to see the county take charge of building any terminal — if it comes to that. That, he said, would ensure it meets county standards.

“They’ll obviously not spend the $10 million that we would spend to do it right,” he said.

The councilman has suggested that Everett or the Port of Everett could help shoulder the financial burden.

Somers said he’s open to hearing Propeller’s idea.

“They seem serious and credible,” he said, “and our attorney who is advising the county on this is familiar with them and says they’re credible.”

Founded in 2008, Propeller has offices in Atlanta and Dublin, Ireland. It’s been involved in developing an alternative to Atlanta’s commercial airport, one of the busiest in the world.

The FAA’s 2012 environmental study of Paine Field likely has a three-year shelf life, agency attorney Lane McFadden said during last week’s court hearing. That would likely give Propeller, or any other party, through the end of 2015 to advance plans for commercial flights. After that, the FAA would have to perform a new study.

Noah Haglund: 425-339-3465, nhaglund@heraldnet.com.