It’s a fish … it’s a plane … it’s a flying billboard!

SEATTLE – For years, thousands upon thousands of fish caught in Alaska waters have ridden quietly, anonymously, in the bellies of southbound Alaska Airlines jets.

You’d think all those frequent fliers would have earned an upgrade.

Now, though they haven’t quite earned a spot in first class, the tons of salmon that have been a steady and lucrative source of income for the airline are finally getting some recognition: a giant king salmon portrait on the side of a plane.

“This airplane celebrates Alaska Airlines’ unique relationship with the people and communities of Alaska and underscores our air transport commitment to the state’s seafood industry,” said Gregg Saretsky, the Seattle-based carrier’s vice president of marketing and planning.

It took a team of 30 painters 24 days to adorn the 120-foot-long Boeing 737 passenger jet with the shimmering likeness. The average 737 takes about a week to paint.

The plane needed a new paint job, as planes do about every four years. Alaska Airlines covered about $75,000 of the tab, company spokeswoman Amanda Tobin said.

The federally funded Alaska Fisheries Marketing Board paid for the rest of the roughly $300,000 project, said Bill Hines, the board’s executive director.

The airline is using the remainder of the marketing board’s $500,000 grant for bookmarks that will be passed out to passengers as part of an educational campaign about the state of Alaska’s fishing industry, Hines said.

Hines, a National Oceanic and Atmospheric Administration official, has led the board since Congress created it in 2003 to give Alaska’s then-struggling salmon industry a boost.

“Three years ago, the salmon industry was at rock bottom. Now demand exceeds supply,” Hines said during a recent tour of the Goodrich Aviation Technical Services plant in Everett, where the plane was being painted.

Alaska Airlines is the only major carrier that flies into and out of many of the remote fishing outposts in southeast Alaska. It expects to fly more than 30 million pounds of seafood from Alaska to the United States, Canada and Mexico this year.

Most of the fish, crab and other seafood caught in Alaska waters is frozen before it’s shipped, in which case there’s no big rush to get it to buyers.

But there’s growing demand for fresh, wild seafood – driven in part by reports about problems associated with farmed fish, including the use of pesticides, antibiotics and other potentially harmful chemicals.

“You can catch a salmon in Alaska waters, and within 24 hours you’ll have it on a plate in New York City. We’re pretty much the only airline that can do that kind of business,” said Matt Yerbic, managing director for the airline’s cargo operations.

Alaska Airlines is spending $15 million to convert five 737-400s to cargo configurations this year. The company expects that will allow it to ship more than 50 percent more fish, mail and other cargo annually.

The one-of-a-kind “Salmon-Thirty-Salmon,” as the airline is calling the specially painted jet, will remain a passenger plane – a move designed to give it maximum exposure to potential seafood consumers.

Mark Boyle, the artist who designed the image, spent about a year working on it and said he’s pleased with how it turned out. “The challenge was to make it anatomically correct and fit the tube of an airplane,” he said one recent morning as a crew prepared to paint the pink scales along the side of the jet.

After a celebration at Seattle-Tacoma International Airport on Saturday, the plane is scheduled to make its first flight to Anchorage today, then hop to Cordova, Yakutat and Juneau.

After that, the plane will fly West Coast passenger routes as far south as Mexico. It will also fly to Denver, Chicago and the Dallas-Fort Worth area.