The captain was sitting a bit tensed in the cockpit. He was fiddling with different instruments, checking on the weather forecast in Dhaka and glancing at his watch from time to time. He then reduced the thrust of the aircraft coming from a Middle Eastern destination.

"It's too early to land in Dhaka," the captain told his co-pilot. "Too much fog and low visibility. Let's fly it easy. Or we have to go on hold or divert."

He landed the flight about an hour behind schedule. But that was hazardous too and that's because Hazrat Shahjalal International Airport is a Category-1 airport, which means pilots cannot land without full visibility.

Unfortunately, winter lowers visibility in Dhaka drastically and then that becomes a big hazard for pilots, airlines and passengers. Every day flights are delayed or diverted.

And yesterday, four international flights scheduled to land at Dhaka morning were diverted to Kolkata because of poor visibility, said Dhaka airport Director AHM Touhid-ul Ahsan.

On Friday, five domestic flights departed after long delays, he said.

"So when a flight is diverted to Rangoon, the airlines have to burn a lot of fuel for no business benefits," a commercial pilot was talking to The Business Standard. "And at Rangoon, it so often happens that food runs out and we can't order food from the airport. Passengers have to go hungry."

So when a plane is diverted, it has to count extra cost for using a different airport and refueling, which makes the airlines profit evaporate as they fly on thin margins anyways. The extra take-offs and landings because of diversion also means extra costs and wear off engines sooner than required.

Today, when the flight from the Middle Eastern city was coming, visibility at Dhaka was around 50 meter and until nine in the morning, it hung at around 200 meters, too low for making any landing because Dhaka requires a minimum 800 meters visibility. 

A pilot has to see the landing visual cues from 261feet height. When today's flight came over Dhaka, the captain could barely see the approach light.

"It was just good enough for me to land," said the captain. "But someone with lesser experience may find it unnerving."

"But why can't we upgrade our airports to Category-2 or 3?" asked another pilot. "Even Kolkata is a Cat-2 airport."

Cat-2 gives more precision in landing. And a Cat-3C airport ensures zero visibility landing.

To upgrade the airport, it will require improving instrument landing system, a highly accurate radio signals navigation aid giving horizontal and vertical guidance to pilots.

One kind of signal gives the glide path and the other shows the runway central line. This gives the pilot accurate bearings of landing.

 

"Another problem we face in winter in Dhaka is that runway 32 lacks an approach light. So we have to land on runway 14," said another pilot.

This means the plane has to make the landing approach from the north and in winter, winds also flow from the same direction.

"This increases our tailwind which makes landing hazardous," said the pilot. "Today when I landed, my tailwind was 7 nautical miles and most aircraft can take up to 10 nautical miles. If we could approach from the south, things would be much easier for us because headwind is no problem for an aircraft. Moreover, we would get better visibility because the sun would be on our back and not glaring right onto our eyes."