When most people think about the busiest air routes around the world, New York to Los Angeles or London to Paris spring to mind. It might come as a surprise to some that the world's most crowded flight path is actually between the South Korean island of Jeju and the capital of Seoul. According to UK-based aviation data monitor OAG, there were 79,460 departures between Jeju and Seoul Gimpo between March 2018 and February 2019. The route's popularity comes from tourism rather than business travel.Jeju is the largest island off the Korean peninsula and it is sometimes labeled "the Hawaii of South Korea". It boasts dramatic volcanic landscapes that have been afforded UNESCO World Natural Heritage Site status as well as impressive hiking trails and stunning beaches. Even though Jeju has lured more international tourists in recent years, particularly from China, the bulk of the visitors are still Korean. In fact, it is so popular among Koreans that there are 200 daily services from Seoul spread between eight different carriers.Across the globe, the ten busiest air routes are all domestic and the connection between Melbourne and Sydney is the second busiest. During the same period, there were 54,102 departures on the 443-mile route between the two Australian cities. Mumbai to Delhi comes third with 45,188 departures. The short hop from Los Angeles to San Francisco is the first American route on the list, coming nonth overall in volume of departures. The busiest international flight path is from Kuala Lumpur to Singapore with 30,187 departures divided between eight different carriers.