SEATTLE -- Horizon Air is discontinuing service to Butte, Mont., and reducing or changing flights to other cities in the Northwest this summer to save fuel and improve financial performance.

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A Horizon Airlines plane.

The Seattle-based regional airline also is phasing out its jets in favor of a single fleet using the 76-seat Q400 turboprop.

Routes affected by service changes include Billings-Portland, Portland-Seattle, Pasco-Seattle, Kelowna-Seattle, Idaho Falls-Boise, Lewiston-Boise, Medford-Portland, Bend-Portland, Bend-Seattle, Billings-Helena, San Jose-Sacramento, Idaho Falls-Seattle, Boise-San Jose, Boise-Sacramento, Wenatchee-Seattle and Seattle-Sun Valley.

Horizon serves 48 cities in the West, including cities in Canada and Mexico.