At least 41 trains were running late and three were cancelled due to dense fog in parts of north India on Monday morning, a railway official said.
According to the Northern Railway official, nine trains were rescheduled.
The cancelled trains included New Delhi-Hyderabad T Express, New Delhi-Vishakhapatnam Express and Anand Vihar-Garib Rath Express.
At least six international and seven domestic flights arriving in Delhi were delayed due to fog, an Indira Gandhi International airport official said.