In 2017, Alaska Airlines will phase out its five Boeing 737-400 "combi" planes that move cargo and passengers primarily around Alaska.

The five combi planes have flown around the state -- Seattle is the only stop they make Outside -- since 2007. Each has space for 72 passengers in the back half of the plane and 6,000 pounds of cargo in the front. These planes were introduced to the fleet to replace several 737-200s, offering the ability to carry 20 percent more cargo and passengers.

They will be replaced with three Boeing 737-700s, which will be converted from all-passenger planes to freighters. It's part of a broader plan to phase out all 26 of the 737-400s in the Alaska Airlines fleet and move toward more fuel-efficient planes.

The work to retrofit those three 700s will start in February. The change is meant to improve the airline's cargo service in Alaska.

"It will allow us to offer a cargo schedule that better serves the cargo needs of the communities we serve in the state of Alaska," said spokeswoman Halley Knigge.

She said, however, that the change isn't driven by heightened demand for air cargo services within the state.

Alaska Airlines Senior Vice President of Communications Joe Sprague told the Associated Press earlier this year that the move is "an opportunity for us to step up our game from a cargo standpoint."

These flights currently operate among Anchorage, Ketchikan, Kotzebue, Bethel, Juneau, Sitka, Nome and Seattle. Combi flights between cities in the southern part of the state are more frequent than those to cities like Kotzebue and Nome.