Lihue Airport (LIH) on the east coast is the only commercial airport on Kauaʻi. Direct flights operate from the US mainland, primarily from Los Angeles, San Francisco, Portland, and Seattle; there are also direct services from Phoenix, Denver, and Dallas. Most other US cities require a connection through Honolulu or another hub. The flight from Los Angeles takes around 5.5 hours.
Inter-island connections from Honolulu (OGG) and Maui (OGG) operate frequently on Hawaiian Airlines and Southwest. If you are combining Kauaʻi with other Hawaiian islands, flying between them is the standard approach — there is no ferry service between the main Hawaiian Islands.
There is no public transport from the airport. Rental cars are available at the terminal from all the major companies; booking in advance is strongly recommended, especially in summer. Taxis and rideshares operate, but a car is essential for exploring the island beyond Lihue.