Thick fog on the western coast, where the airport is situated, also caused 312 delays and 49 cancellations Saturday. The IIAC said 43 other flights bound for Incheon were forced to land at other airports in the country.

An IIAC official said delayed or canceled flights from Saturday have caused a logjam on Sunday, and it won’t be until late afternoon that the operations will be back to normal.

The Aviation Meteorological Office issued a low visibility warning at Incheon International Airport at 1:35 a.m. Sunday and lifted it some four hours later.

This type of warning is issued when the visibility is under 400 meters, and the visibility at the airport dropped to 50 meters at one point Saturday.

While the airport officials were grappling with fog, other parts of the country were blanketed by ultrafine dust Sunday.

The Korea Environment Corp. issued an ultrafine dust (PM-2.5) advisory Saturday afternoon, and it remained in effect in Seoul, Incheon and other regions as of 10 a.m. on Sunday.

The advisory is issued when an hourly average ultrafine dust concentration of more than 90 micrograms per cubic meter (㎍/㎥) is expected to last for two hours and is lifted when the hourly average concentration falls below 50 ㎍/㎥.

As of 10 a.m. on Christmas Eve, the average concentration per hour in Seoul was 66 ㎍/㎥, 55 ㎍/㎥ in Busan and 56 ㎍/㎥ in Incheon.

The Korea Environment Corp. said the continued rain is expected to wash away some of the fine dust and the concentration level should drop later Sunday. (Yonhap)