Flight operations at Delhi airport were affected today as dense fog brought down visibility in some parts of the national capital to zero. Passengers have been advised to contact their respective airlines for updates on their flights. "While landings and take-offs continue at Delhi Airport, flights that are not CAT III compliant may get affected. Passengers are requested to contact the airline concerned for updated flight information. Any inconvenience caused is deeply regretted," reads the advisory issued by Delhi Airport.