Nearly 40 flights including some to international destinations were delayed as dense fog engulfed the Indian capital Delhi early Sunday.
At least 30 domestic and 10 international flights were affected, according to officials at the Indira Gandhi International Airport, dpa reported.
Runway visibility was less than 125 metres for most of Sunday morning, and flights began to take off only after the heavy fog started to lift around noon.
Airport officials said visibility should be at least 150 metres for a plane to take off or land.
Five international flights coming from Dubai, Singapore and Beijing and an equal number number of flights departing for international destinations were delayed by up to three hours.
The Delhi airport had been experiencing thick fog since Wednesday night, affecting the schedules of 350 flights, causing inconvenience to air travellers.
Railways officials also had to delay or cancel about 50 trains in Delhi and the northern region due to the conditions.
Vehicular traffic in the city was also affected by the poor visibility. At least 20 people were injured when 15 cars crashed in an accident blamed on fog in the Delhi suburb of Noida on Saturday.