Hawaii Magazine reports that, as of December 21, 2017, Delta Airlines added a daily non-stop flight to Lihue, Kauai from Seattle. Delta joins Alaska Airlines in serving Kauai from Seattle, giving travelers another option to consider.
As of now, the following mainland U.S. cities all offer non-stop connections to Lihue, Kauai:
Denver, Colorado: United Airlines
Los Angeles, California: Alaska Airlines, American Airlines, Delta Air Lines, United Airlines
Oakland, California: Alaska Airlines
Phoenix, Arizona: American Airlines
Portland, Oregon: Alaska Airlines
San Diego, California: Alaska Airlines
San Francisco, California: United Airlines
San Jose, California: Alaska Airlines
Seattle, Washington: Alaska Airlines, Delta Air Lines
Also, if you’re looking for a connection from Canada, WestJet Airlines offers a non-stop connection from Vancouver, Canada.