The combined value of unused miles at South Korea's two major air carriers reached 3.4 trillion won ($2.5 billion) as of the first half of 2023, data showed Sunday, amid the extension of expiry dates after the COVID-19 pandemic disrupted international travel.

The amount of the deferred income of the two companies, Korean Air and Asiana Airlines, which can be translated into unredeemed miles, marked a 17.4 percent rise from the same period in 2019, according to the companies' regulatory filings.

Korean Air accounted for 2.4 trillion won, with Asiana Airlines taking up 942 billion won.

During the COVID-19 pandemic, the government reached an agreement with the air carriers to extend the expiration by three rounds up to 30 months.

Local airliners have operated an expiration policy on mileage points since 2008, and starting 2019, these points have started to expire.

The air carriers, meanwhile, have been rolling out promotional events to induce consumers to use their unredeemed miles, apparently in line with efforts to reduce debts ahead of their planned merger.

Earlier this month, Korean Air increased the maximum amount of redeemable miles to 30 percent from the existing 20 percent. (Yonhap)