The Fair Trade Commission has approved the merger of Korean Air and Asiana Airlines, on the condition that the country's top two airliners promote fair competition with other carriers.

The antitrust regulator announced Tuesday it granted conditional approval to Korean Air's proposal to buy a nearly 64-percent stake of debt-laden Asiana Airlines, stipulating that the two companies transfer take-off or landing slots and flight licenses where deemed necessary for fair competition. The conditions are to remain in effect for ten years from the day the merger is completed.

Korean Air and Asiana Airlines will be mandated to transfer domestic airport slots to other carriers seeking to operate on 26 international and eight domestic flight routes, including New York and Guam-bound flights from Seoul, and Qingdao-bound flights from Busan. The two firms must also surrender flight licenses required for 11 of those flight routes if other carriers are seeking to operate on those routes.

After evaluating 119 international and domestic flight routes that overlap with competitors, the antitrust watchdog concluded that 40 routes may be exposed to limited competition after the merger and prohibited the airlines from raising flight fares.

The Fair Trade Commission plans to fix administrative measures of the merger once the proposal is reviewed by regulators in the U.S. and five other countries with airlines that may be affected by the merger.