The airline began to diversify its fleet during the beginning of the decade by introducing larger aircraft. In 2013, Jin Air took delivery of its first Boeing 777-200ER, becoming the first low-cost carrier in Korea to operate widebody aircraft. These aircraft, configured in high-density single-class layouts, enabled Jin Air to operate high-capacity routes to popular leisure destinations such as Guam, Bangkok, and Honolulu.

By 2015, Jin Air had established itself as a significant player in the Korean low-cost market. The airline continued to expand its network across Japan, China, Southeast Asia, and the Pacific. Routes to Japanese cities such as Osaka, Fukuoka, and Okinawa were particularly important, given the strong bilateral tourism flows between South Korea and Japan. Similarly, Jin Air expanded into secondary Chinese cities, capitalizing on the liberalization of air services agreements between the two countries. Fleet growth continued with additional Boeing 737-800 aircraft, allowing the airline to increase frequencies and open new routes while maintaining operational flexibility.

In December 2015, the airline launched flights between Seoul Incheon and Honolulu using its Boeing 777-200ER fleet. This marked Jin Air’s entry into true long-haul low-cost operations and positioned it as a pioneer among Korean budget airlines. Around the same period, Jin Air also strengthened its presence in Guam, increasing frequencies and solidifying its position as a leading carrier on that route.

However, the airline’s growth trajectory faced challenges in the late 2010s. In 2018, Jin Air became embroiled in a regulatory controversy involving its parent company, Korean Air, and the Cho family, which controls the Hanjin Group. It was revealed that a foreign national had been registered as a director of Jin Air, in violation of South Korean aviation laws. As a result, the Ministry of Land, Infrastructure and Transport imposed sanctions on the airline, including a ban on adding new aircraft and launching new international routes. This restriction significantly slowed Jin Air’s expansion during a period when competitors were continuing to grow. The airline was forced to focus on optimizing its existing network and improving operational efficiency rather than pursuing aggressive expansion.

The restrictions remained in place until March 2020, when they were lifted after Jin Air implemented governance reforms. However, almost immediately afterward, the global aviation industry was hit by the COVID-19 pandemic, which caused an unprecedented collapse in passenger demand. Jin Air, like other airlines worldwide, was forced to drastically reduce its operations, suspend many international routes, and rely heavily on domestic services, particularly the Seoul–Jeju corridor.

As travel restrictions began to ease in 2021 and 2022, Jin Air gradually resumed international flights, initially focusing on short-haul routes to Japan and Southeast Asia where demand recovered more quickly. The airline also reinstated services to Guam and other leisure destinations, which were among the first to see a rebound due to pent-up travel demand. Fleet utilization improved as more aircraft returned to service, and Jin Air resumed plans for network expansion, although with a more cautious and phased approach compared to the pre-pandemic era.