Police investigators inspect the scene of the deadly crash of a Jeju Air passenger jet at Muan International Airport in South Jeolla Province, Thursday. Yonhap

Korea's low-cost carriers (LCCs) heavily rely on overseas outsourcing for maintenance, repair and operations (MRO) due to limited in-house capabilities, according to data and industry officials on Thursday.

According to the Ministry of Land, Infrastructure and Transport, LCCs spent 502.7 billion won ($342.34 million) for overseas aircraft maintenance in 2023, up 63.6 percent from 2019.

The portion of aircraft sent to other countries for MRO also increased to 71.1 percent, up 14.3 percent during the same period.

This sparks concerns over the shortage of domestic aircraft MRO facilities. Only two companies, Korean Air and the Korea Aerospace Industries Association (KAEMS), operate such facilities.

The issue has come under scrutiny following the deadly crash of a Jeju Air passenger jet on Sunday, which left 179 of the 181 people onboard dead. Jeju Air is Korea's largest LCC.

Industry officials are urging the government to develop relevant measures to train MRO technicians, as LCCs lack the financial resources to do so, unlike other full-service carriers like Korean Air.

"It is realistically impossible for LCCs to build their own MRO facilities for financial reasons," an aviation industry official said.

"The government should make policy wise efforts to back up the growth of the relevant industry here."

The head of Jeju Air also said that most of its passenger jets are sent abroad for heavy maintenance.

"We carry out daily maintenance operations on our own but outsource heavy maintenance to overseas MRO firms," Jeju Air CEO Kim E-bae said at a media briefing.

"KAEMS has only a limited number of maintenance slots, so we sent only a few aircraft to the company, and the rest is outsourced to foreign firms."

In August 2021, the land ministry announced a series of measures to boost the domestic aviation MRO industry. At the time, the authority said it would increase the portion of domestic aircraft MRO services to 70 percent by 2025. However, this is highly unfeasible given LCCs' growing reliance on overseas MRO providers.

Jeju Air reported three aircraft safety incidents last year, second only to T'way Air with eight cases during the same period.

The average age of aircraft operated by Jeju Air is the highest among Korean LCCs at 14.4 years, followed by T'way Air at 13 years and Jin Air at 12.7 years, according to Aviation Technical Information System data.