Dense fog once again played havoc with the schedule of around 175 flights at the Indira Gandhi International airport on Friday.Around 144 flights were delayed, 10 were cancelled and four were diverted as fog enveloped the airport early Friday morning. Flights were delayed by upto five hours, causing inconvinence to passengers.Two Jet Airway flights from Doha and Abu Dhabi and one Kingfisher flight from Dubai were diverted to Jaipur while one BlueDart cargo flight from Chennai was diverted to Ahmedabad.Three flights were cancelled due to inclement weather conditions at Delhi , three others due to poor weather at destination and four others by the airlines due to operational reasons.