India, Dec. 31 -- Dense fog disrupted road, air, and train traffic, prompting the cancellation of 148 flights on Wednesday, even as Delhi's air quality remained very poor and was expected to deteriorate to the "severe" category. The mercury plunged to 6.4degC, which is around normal, compared to 9.4degC the day before.

The visibility dipped to 50 metres at Palam and remained in this range for close to four hours. "At Delhi, visibility was 50 metres at Palam between 4am and 8am," said an official. This disrupted air traffic at the Delhi airport, which included two diversions.

Over 550 flights were delayed at the Delhi airport on Tuesday. Airport officials said 118 flights were cancelled and 16 were diverted due to adverse weather conditi...