South Korea’s Ministry of Transport has warned the country's six budget carriers to adhere to safety regulations or face possible action. The warning followed a safety review of the airlines after two recent incidents involving separate carriers. In the first, a Jin Air 737-800 en route from Cebu in the Philippines to Busan, South Korea, turned back after 40 minutes due to an air leak in one of its doors. The airline operates as a wholly owned subsidiary of Korean Air.

In the other, a Jeju Air 737-800 flying from Seoul to Jeju plunged 10,000 feet due to a malfunctioning cabin control pressurization device. The aircraft landed safely at Jeju International Airport.

According to Jim Hae, a Ministry of Transport official in Seoul, budget carriers should invest more in safety given the rapid growth in traffic over the past 10 years.

The airlines in question accounted for a 59 percent share of the crowded domestic market in 2015.

Hae said the ministry will revoke the operating certificates of any airline that fails to ensure safety.

The Ministry of Transport decided to suspend ground crew and the pilots involved in the incidents for 30 days after investigations revealed that they appeared to have ignored basic safety procedures. The two airlines also face suspension of their operations for a week or a fine equal to $496,000.

The other budget carriers that received the warning are Eastar Jet, T'way Airlines and Asiana-owned Air Busan and Air Seoul. Asked whether the warnings suggest lax safety practices at those four airlines, Hae characterized the two incidents as “isolated.”