The state antitrust agency has rejected a mileage integration plan proposed by Korean Air as part of its merger with Asiana Airlines and has asked Korean Air to immediately revise and supplement the proposal.

The Fair Trade Commission(FTC) said Thursday that there were shortcomings in the proposed mileage redemption compared with what Asiana previously offered.

The FTC said the submission was deemed insufficient for a formal review in terms of offering an explanation on the mileage integration ratio.

While the details of the plan were not disclosed, there is speculation that the proposed mileage integration ratio was considered unfavorable to Asiana’s customers, with the market value of its miles estimated at roughly 70 percent that of Korean Air miles.

The mileage integration is a key condition for approval of the two carriers’ merger, with Korean Air, which signed a deal in 2020 to acquire a controlling stake in Asiana Airlines, required to submit the integration plan by Thursday.

The FTC’s rejection of the proposal is expected to delay the final authorization process, which means the two carriers’ corporate integration launch could also be postponed beyond October 2026.