By 2040, demand for commercial air travel at Paine Field could quadruple from what it was pre-pandemic, according to a new forecast.

The annual passenger count could swell to 4.3 million over the next two decades, compared with about 1 million in 2019, says a report commissioned by Snohomish County as part of an effort to draft a new long-term plan for the airport.

The passenger terminal at Snohomish County-owned Paine Field would have to open four more gates to meet that demand, said Michael Tubridy, vice president of master planning for Landrum & Brown, the aviation consulting firm that prepared the forecast.

Built and run by the private company Propeller Airports, the terminal opened in 2019 with two jet bridges and a third gate that allows passengers to board planes from the pavement.

Now the county will consider setting aside land to make it bigger.

“As traffic continues to grow, some of the existing facilities will need to be expanded or improved,” Tubridy said at a virtual public meeting last week.

The forecast comes as local and state leaders explore options for meeting future air travel demand in the Puget Sound region, and as Seattle-Tacoma International Airport gets busier. The number of passengers is expected to outstrip the region’s capacity in the next decade or so, as demand for flights rebounds from the pandemic.

Washington officials are already eyeing Paine Field to meet the need. This year, the Everett airport made a state commission’s short list of airports that are good candidates for expansion in the next 20 years.

With the airport master plan, the county will assess what’s physically and financially possible and — with input from the public — outline the best route forward.

Any proposed terminal addition is likely to draw intense scrutiny from neighboring communities, who fought passenger service for years and ultimately lost in court.

Propeller CEO Brett Smith said he’s now focused on weathering the pandemic and recovering — not expanding.

“We look forward to working with the county and all stakeholders as we go through the master plan process,” he said in an interview Friday with The Daily Herald.

The county will have to weigh other rising demands the airport faces, too, including the need for more facilities for general aviation and air cargo operations, the forecast shows.

“I view it as like a big jigsaw puzzle. And how do we fit it in together,” county Aerospace Economic Development Director Terry Ryan said at the meeting. “That’s what the master plan process is for.”

Already, there’s need for more hangar space at the airport to serve businesses and people who lease spots for their aircraft, according to an inventory prepared for the master plan. There are more than 230 potential tenants on a waiting list for the county-owned spaces, including nearly 300 hangars and 55 storage units. Most of those people can expect to wait more than two years for an opening, the inventory says.

The airport is known as the home of the Boeing Co.’s Everett plant. The airfield hosts more than 60 other businesses, too, including Aviation Technical Services, which specializes in commercial airplane repair and renovation. FedEx Express recently launched cargo operations at the airport after taking over Boeing’s Dreamlifter Operations Center, previously used for transporting model 787 components. There are also flight schools, museums, educational institutions and government offices.

While most of the roughly 1,300-acre airport is occupied, about 120 acres on the west side are undeveloped.

In the next phase of the master plan process, the consultant will work with the airport on options for how the airfield could change in the future. Those proposals will be released for public comment next year. Once a preferred option is chosen, the county will study the environmental impact and financial viability.

The county has formed three primary committees to guide the plan’s development. A steering committee is made up of county directors, business leaders and the executive director of the Port of Everett. Members of a “stakeholder advisory committee” include a wide range of people with interest in the airport’s future, including Smith and representatives from Boeing. Senior airport staff and the consulting team make up a third, “technical committee.” There’s also the Snohomish County Airport Commission, created in 2017 to make recommendations for the master plan and advise the county executive on other issues related to the airport.

As part of the process, the airport is holding a public comment period that ends Nov. 24. People can comment online at painefieldmasterplan.com. There’s also a virtual public meeting at 11 a.m. Tuesday.

The plan is expected to be made final in the spring of 2023. It requires approval from the Snohomish County Council and the Federal Aviation Administration, airport spokeswoman Kristin Banfield said.

The consultant has so far ruled out the need for another runway at the airport. Almost everything else is still on the table. Improvements to be considered include upgrades to taxiways, access roads and other paved surfaces.

Based on a 2018 environmental assessment conducted before the start of scheduled passenger service, Paine Field is limited to 24 daily departures and 24 arrivals. But with more planning and an environmental review, “it could accommodate more,” the report concludes.

Before the pandemic, demand for air travel in the Puget Sound region was expected to exceed available capacity by 2027. But the global crisis has dealt a devastating blow to aviation industries.

The new forecast predicts that demand for passenger service at Paine Field will recover in 2025. Under the prediction, one passenger represents each time a person gets on or off a plane.

The number is expected to surpass 1.5 million in 2030, then climb more rapidly in the late 2030s as Sea-Tac Airport reaches the limit of what it can handle without new improvements, according to the forecast.

“We do not have an opinion on the specific constraints at Sea-Tac or the timing of those constraints. Our focus is strictly on PAE,” Tubridy said in an email, referring to Paine Field’s three-letter airport code. “The PAE forecast takes into account the impacts of the pandemic to aviation as a whole, including passenger service.”

Any growth of Paine Field’s passenger service will also depend on whether terminal operator Propeller can attract commercial airlines. United Airlines announced last July it would discontinue service here.

The terminal’s sole remaining carrier, Alaska Airlines, recently delayed a plan to add more flights to its schedule at the airport as the COVID-19 Delta variant surged. The airline now expects to operate up to 12 departures per day from Paine Field starting Jan. 4, a company spokesman told The Herald last month.

Smith, Propeller’s CEO, said he expects passenger demand will return to pre-pandemic levels before 2025.

“We think we’ll be back up by the end of next year,” he said, with a caveat.

“I’ve started to get out of the fortune-telling business at this point. Because nobody knows what’s going to happen.”

Rachel Riley: 425-339-3465; rriley@heraldnet.com. Twitter: @rachel_m_riley.

More on the Airport Master Plan

Register for a virtual webinar on Tuesday, Nov. 9, from 11 a.m. to noon.

Learn more and submit written comments at painefieldmasterplan.com.