Engineers from Jin Air and Boeing jointly conducted the repair and replacement work on structural cracks on the B737-NG plane in the past two weeks, the company said in a statement.
The US Federal Aviation Administration and the Ministry of Land, Infrastructure and Transport have approved the outcome of the repair work after safety checks and test flights, it said.
"The Boeing team, together with Jin Air engineers, is working on Jin Air's two other B737-NGs (with the same problems) and the repair work is expected to finish within this year," a company spokeswoman said.
Last month, the authorities discovered structural cracks on 13 B737-NG planes and have since grounded them. A team of US engineers flew to South Korea on Oct. 31 to help fix the problems.
The 13 planes include five from Korean Air Lines Co., three from Jin Air Co., three from Jeju Air Co. and two from Eastar Jet.
The US team is now working on the five planes operated by Korean Air and two of the three by Jin Air.
In early October, the FAA ordered aircraft operators to conduct checks on B737-NG airliners for structural cracks after Boeing discovered cracks on an aircraft undergoing modifications in China and notified the FAA of the issue.
South Korea has two full-service carriers -- Korean Air and Asiana Airlines Inc. -- and seven low-cost carriers -- Jeju Air, Jin Air, Air Busan Co., Air Seoul Inc., Eastar Jet, T'way Air Co. and Fly Gangwon.
Asiana Airlines and its two budget carriers, Air Seoul and Air Busan, do not operate B737-NG planes in their fleets. (Yonhap)