Heavy fog disrupted flight operations at the Delhi airport on Monday with 20 flights diverted, four cancelled, and around 530 delayed till 12.52 pm, according to news agency ANI. The 530 delayed flights include 320 departures and 210 arrivals approximately. Flights are operating at the airport under CAT III B conditions, which means the runway visual range is between 50 metres and 175 metres. All airlines have requested passengers to check flight status before leaving home and reach out to its customer care. Train travellers were also hit due to the fog with thirty trains were delayed by two to seven-and-a-half hours.