EVERETT — If Snohomish County refuses to bend to accommodate an airline that wants to fly out of Paine Field, the federal government will pull its funding for runway improvements and other airport projects.

The warning was issued this week in a letter from the Federal Aviation Administration to the county, which owns and operates the airport.

Allegiant Air, a Las Vegas-based airline, wrote the county last month expressing interest in running two to four flights per week from Paine Field to Las Vegas.

County Executive Aaron Reardon and three of the five County Council members quickly opposed the plan. They wrote a letter to Allegiant Air saying the county would not pay for any improvements to the airport’s small terminal or other facilities to help the airline.

This week, the council voted 4-1 for a resolution officially opposing the plan.

“Failure to negotiate in good faith may subject the county to an enforcement action,” wrote Carol Key, manager of the Seattle Airports District Office of the Federal Aviation Administration. “To comply with your grant assurances and ensure continued receipt of federal funding, you must negotiate in good faith with Allegiant Air.”

The letter was dated Wednesday, the same day the County Council passed its resolution.

The federal government has spent $52 million on the airport since 1945. That gives federal authorities leverage over how the airport is used.

Airport operators who take federal funds are prohibited from discriminating against any type of aviation use, including commercial service. While an airport operator is not obligated to pay for improvements to accommodate an airline, they must provide space if it’s available, Key said Friday.

“They have to provide the space for them to initiate service,” she said. “That doesn’t mean you have to build them a terminal.”

In this case, getting the airport ready for passenger flights could take as little as moving a modular building in to serve as a terminal. Allegiant Air has yet to respond to the county’s original refusal letter.

Key said the only case she knows of in which an airport refused passenger air service was Centennial Airport in the Denver suburbs, one not unlike Paine Field. In the 1990s, Arapahoe County, the airport’s operator, voted twice to ban commercial service. As a result, the airport had its funding pulled.

“They are now back in compliance,” Key said. “They changed their minds. They needed their runway reconstructed.”

Even so, the airport kept commercial passenger service out.

Snohomish County remains opposed to passenger service despite the FAA’s letter, said Christopher Schwarzen, a spokesman for Reardon.

“But we have every intention of following the law,” Schwarzen said. “And the FAA in its letter points out certain legal obligations to us, and we are reviewing those obligations now.”

The cities of Mukilteo, Edmonds, Lynnwood, Mountlake Terrace and Woodway have fought any suggestion of passenger service at the airport, which today primarily serves smaller private planes and Boeing operations. They contend noise from more flights would harm neighborhoods and interfere with other business at the airport.

Others, including some county business leaders, favor air service, saying it would be good for the area’s economy.

Snohomish County Councilman Brian Sullivan said he plans to enlist the help of some of the state’s congressional delegation. He’d like to have a meeting with them soon in Washington, D.C.

“This will always be a battle,” he said.

Sullivan noted that King County successfully turned down Southwest Airlines’ proposal in 2005 to build a terminal and run flights out of Boeing Field in Seattle. Key noted that Alaska Airlines also was involved in the proposal, and King County showed it could not accommodate both carriers at Boeing Field.

“That doesn’t make sense to me, because they would have to say yes to one or the other,” Sullivan said.

County Councilman John Koster was the lone “no” vote in last week’s resolution.

“This has been one of my main concerns with doing the resolution, was jeopardizing those grants,” Koster said.

“You can’t respond in a fashion that’s knee-jerk,” he said. “You have to negotiate in good faith and the FAA validated that in the letter.”

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