What is the fine-grained topic of the following text: The airport is served by six major airlines that offer direct flights to 21 nonstop destinations, including; Chicago, Denver, Dallas/Fort Worth, Houston, Las Vegas, Lewiston, Los Angeles, Minneapolis, Oakland, Phoenix, Portland, Reno-Tahoe, Sacramento, Salt Lake City, San Diego, San Francisco, San Jose, Seattle and Spokane, with connecting flights to thousands of cities worldwide. Only return the topic.
Airport's airline services and destinations