<prompt> Kuzalisha toleo ngumu zaidi ya sentensi hii Wabebaji ni pamoja na Horizon Airlines, Skywest Airlines kuruka kama wote United Express na Delta Connection na Allegiant Airlines.  <response>: Bila shaka, toleo ngumu zaidi ya sentensi ni Carriers ni pamoja na Horizon Airlines, Skywest Airlines kuruka kama wote United Express na Delta Connection na Allegiant Airlines kutoa huduma ya moja kwa moja kwa Portland, Seattle, Salt Lake City, San Francisco, Las Vegas na Mesa, Arizona. 