Thick fog on Thursday hit air traffic in Delhi, with all flights getting delayed and some international flights diverted to other cities.

While in general the fog reduced the visibility to around 200 metres, the visibility on the runway at the domestic and international airports went down to as low as 50 metres around 0630 IST.

As a result of the low visibility, no flights could take off or land for around two hours since 0630 IST, airport sources said.

Five Lufthansa flights were diverted to other cities during this time, they said.

After 0900 IST, however, the visibility started improving and flights began taking off, but there was a delay of around two to three hours.

CAT 3 B instrument landing system had been activated since 0620 IST, the sources said.

Due to foggy conditions in North India, trains arriving in Delhi were also delayed by as much as six hours, while early morning motorists went slow due to the fog.