Japan Air System plans to stop operating international flights to and from Kansai International Airport in Osaka Prefecture when the second runway at Narita airport outside Tokyo opens in April, JAS sources said Saturday.

JAS is also considering suspending most of its domestic flights to and from Kansai airport when Tokyo's Haneda airport increases its number of landing slots in July, the sources said.

JAS's effective withdrawal from Kansai airport is likely to deal a serious blow to the airport's operator, Kansai International Airport Co., as JAS accounts for nearly 10 percent of the airport's revenues. The move could also affect the fate of the airport's ongoing expansion plans.