Fog-induced poor visibility at Birsa Munda Airport here led to the diversion of three flights early on Thursday morning.

The flights were diverted to Calcutta as visibility was down between 600 metres and 800 metres at the Ranchi airport from 6am to 9.30am. When visibility improved to 1,300 metres after 10pm, the flights came back from Calcutta and were allowed to land in Ranchi.

Among the three diverted flights, two were from Delhi while another was from Calcutta.

“There was an Alliance Air (the wholly owned subsidiary of Air India) flight from Calcutta that couldn’t land here and returned to Calcutta,” Vinod Sharma, director of Birsa Munda Airport, told The Telegraph.

“The other two flights, each operated by GoAir and IndiGo, which were diverted to Calcutta, had been coming from Delhi,” Sharma added. “Visibility was insufficient for landing in the morning, so we had no other option but the detour. However, the flights returned when visibility improved.”

Aircraft landing and subsequent taxiing can be extremely risky for the pilot in case of dense fog and low visibility.

According to the local meteorological department, dense fog had reduced the visibility at the airport to 800 metres from 6am to 7.30am.

Visibility dropped further to 600 metres by 8am and continued to be the same till it improved slightly to 800 metres again at 9.30am, the Met office said.

However, it went up to 1,300 metres by 10am.

Improved visibility allowed landing of aircrafts and the diverted flights returned to Ranchi again.