Dense fog on Thursday snarled post-Christmas travel at both Green Bay's Austin Straubel Airport and the Appleton Airport, canceling multiple flights.As of 5 p.m., four arriving flights had been canceled at Austen Straubel, and six flights nixed at Appleton, according to the airports' flight status webpages.Numerous departing flights at both airports were also scrubbed or delayed.The National Weather Service has issued a dense fog advisory until noon on Friday.