South Korea's largest low-cost carrier Jeju Air said it needs more time to conduct due diligence on Eastar Jet, causing a delay to its purchase of the budget carrier.

Jeju Air signed a preliminary deal in December to buy a 51% stake in Eastar Jet Co for 69.5 billion won ($60 million). It had been due to complete before Jan 9.

"The process will be extended to the end of January, along with the schedule for the signing," a company spokesman was quoted a saying by the Yonhap News Agency.

The proposed deal could help alleviate the clogged domestic market which is one of the reasons cited in the recent struggles of the South Korea aviation industry.

South Korea's Ministry of Land, Infrastructure, and Transport, which will host the 2020 Asian Aviation Education and Training Symposium in Seoul in 18-19 June, has brought about new measures to help boost the industry.