The visibility dropped to zero metres at Palam area between 6:30 am and 7:30 am. “Fog Alert – Low Visibility Procedures have been implemented at Delhi Airport… Passengers are requested to contact the airline concerned for the updated flight info,” the official Twitter handle of the Indira Gandhi International Airport stated. Runway visibility of upto 50 metres is required for an aircraft to land, it said.Airlines such as Vistara and IndiGo have put out travel advisories asking passengers to check their flight status before heading to the airport. Jet Airways said a few of their flights at Delhi, Bengaluru and Bhopal have been affected due to fog. Vistara also said flight delays are expected in Bengaluru and Delhi.