The Des Moines airport will have to aggressively lobby for more flights if it is to reach the 3 percent annual growth in passenger traffic needed to support a proposed $420 million project that includes a new terminal and related improvements, airport Executive Director and General Manager Kevin Foley told the airport board Tuesday.

“We are in desperate need of more seats,” Foley said. “Most of our flights are nearly at capacity.”

If the passenger traffic doesn’t grow by 3 percent or so a year, the terminal construction may be delayed, airport officials have said.

Growth has been well above 3 percent the past few years, but seems to have slowed to between 2 percent and 3 percent in recent months. Foley said that May’s passenger numbers will be available from the airlines this week, but that they seemed a bit soft. June has been busier so far, he noted.

Still, Foley said many of Des Moines’ current flights are nearly full. With airlines eyeing an industrywide boost of just 5 percent in seats, and Wall Street battering the companies’ stocks, Des Moines will have fierce competition for new flights, he added. Business executives have long pushed for more flights to help spur economic development.

Foley previously noted that most airlines don’t expect to add new aircraft until next year. Plans appear to be for bigger jets, which could help airlines’ bottom line but might mean fewer flights on existing routes in Des Moines.

That’s why Foley again was pitching Des Moines to airlines recently. He had his first meeting with Alaska Airlines, hoping to gain service to western states. He also met with National Airlines, a relatively new charter line that is moving to a model similar to Allegiant Airlines’ to offer scheduled service. He has continued to lean on Southwest Airlines to offer flights to St. Louis.

The recent Delta announcement that it will offer flights to Salt Lake City on 76-seat jets beginning Sept. 1 will help, Foley said.

Airport board member Mark Feldmann noted that Southwest Airlines’ addition of flights to Las Vegas “drastically improved” service to western U.S. markets. Foley agreed, but said Des Moines still needs more flights.

Foley said most Des Moines passengers are heading to western destinations, some of them with a stop in Chicago. When bad weather leads to delayed or canceled flights in Chicago, things can get messy quickly, he added. “We need more hubs,” especially in the western states, he said.

The Des Moines airport could use more flights to many markets, Foley said.

He noted that Delta has been filling about 92 percent of its seats for flights to Atlanta. Because traffic is lighter on the weekends, that means the airline is probably turning away customers during the week, he added.

The Des Moines airport is overhauling its incentives program, and Foley decided to tinker some more after discussing the matter with officials from various airlines in Seattle. The airport board is expected consider a new package soon.

For example, with Wichita’s  program to give subsidies for Southwest Airlines reportedly on the way out, Foley said, Des Moines might be in a position to persuade the company to expand its flights from Des Moines. “They are probably pulling planes in Wichita,” he said of Southwest. “We’ll tell them, ‘You need to put one in Des Moines.’ It’s that simple.”