More than 50 flights, both domestic and international, were either delayed or cancelled Monday morning from New Delhi\'s Indira Gandhi International Airport, after dense fog enveloped the Capital city. According to Airport sources, runway visibility started to deteriorate from late Sunday and general visibility reduced to less than 100 meters by Monday morning, leading to delay in departures of early morning flights. The general visibility on the main runway was almost zero while the runway visibility was 75 meters. At one time the runway visibility dropped to zero at one end of the third runway, said the Airport sources, adding that the operations at the third runway remained suspended for major part of the morning due to poor visibility. Meanwhile, the Meteorological Department has predicted dense fog till Christmas. On Sunday also, over 100 flights were badly affected due to dense fog