Bengaluru, Dec 28 (IANS): Heavy fog and poor visibility may delay arrival and departure of domestic and international flights at Bengaluru airport on Sunday morning, an official said on Saturday.

"Safe landing and smooth take-off of aircraft on time depend on visibility in the early morning on any given day. The city weather is unpredictable and sudden heavy fog reduces visibility of the runway for pilots to land or take-off," an official of the Kempegowda International Airport (KIA) told IANS here.

As the vicinity around the airport at Devanahalli, about 40 km north of the city centre, was free from fog on early Saturday, there were no delay in arrival or departure of about 60 flights between 5 a.m. and 8 a.m.

"Poor visibility, however, on Friday due to early morning fog disrupted flight schedule of 67 aircraft, including 38 departures and 29 arrivals," recalled the terminal duty manager.

As a result, five city-bound aircraft were diverted, including three to Hyderabad and two to Chennai for safety reasons, as thick fog in the wee hours engulfed the sprawling airport, including its two runways.

Though the airport operator Bangalore International Airport Ltd (BIAL) has built the second runway with CAT III instrument landing system, it has not been made operational due to delay in regulatory clearances.

As the third busiest airport in the country after Mumbai and New Delhi, Bengaluru is connected to about 60 domestic and overseas routes for ferrying passengers as well as freight.

"Air traffic movements average 500 per day in all-clear weather, with most flights in the early morning and late night hours," the official added.

Unlike other bigger airports across the country, the Bengaluru airport is situated at about 3,000 feet above the mean sea level.