The best price found from United States to Busan is on April 24th, 2017, travelling with Air China. See more options, compare prices and book: search flights.
There are frequent international flights to Japan and regional cities such as Beijing, Hong Kong, Bangkok, Chiang Mai and Cebu.
On domestic routes, the Busan–Seoul flight on Korean Air, Asiana or AirBusan (one hour, every 30 minutes from 7am to 9pm) usually requires reservations on weekends and holidays. Most flights from Busan to Seoul land at Gimpo airport, which has few international connections. If you’re flying out of the country, catch the A'rex, which runs between Seoul station and Incheon International with a stop at Gimpo airport. Flights also connect Busan and Jeju-do (one hour, every 30 to 90 minutes from 7am to 8pm).