A dense fog and severe cold continue to grip northern India, causing major disruptions to air and rail traffic.
At least 170 flights have been affected since Tuesday night when thick fog descended on the capital, Delhi. Hundreds of trains have been delayed.
Road traffic in the city is crawling with visibility reduced to less than 50m (165ft) in many places.
More than 450 people have died from the cold, with most deaths reported from the northern Uttar Pradesh state.
Fog continues to hit flight operations at Delhi's Indira Gandhi International airport for the second consecutive day on Thursday, news agency Press Trust of India reports.
"Since last night 27 domestic and international flights were diverted, 18 were cancelled and around 20 have been rescheduled as thick fog blanketed the airport reducing the runway visibility to 150 metres or less," PTI quoted an airport official as saying.
Some of the morning flights are delayed by over two to three hours and thousands of passengers are stranded at the airport.
All flights to the city of Jaipur from Delhi have been cancelled and passengers said no taxi drivers are willing to drive there because of the fog.
India's national carrier, Air India, said its flights to New York and Frankfurt, which were scheduled for Wednesday night, will leave on Thursday morning.
An Emirate Airline flight to Dubai from Delhi was delayed for about 15 hours due to bad weather conditions.
The fog, which descended on Tuesday night, has played havoc with the railway traffic too.
On Wednesday, 45 trains were cancelled, 35 rescheduled and 24 delayed because of the weather conditions.
Road traffic is slow-moving and motorists are using their hazard lights.