Afghanistan conflict: The Air India flight out on a fateful Sunday

Passengers on the Air India flight from Kabul landed in Delhi on Sunday evening

When an Air India flight carrying 40 passengers - all Afghans - from Delhi approached the airport in Kabul on Sunday afternoon, air traffic control cleared it for landing.

It was a warm, sunny day with temperatures rising to 35C.

The six-member crew had little idea of how fast things were unravelling on the ground. Taliban fighters were seizing Kabul after the government in Afghanistan collapsed, bringing to a swift end almost 20 years of a US-led coalition's presence in the country.

Even as the pilot prepared for landing, air traffic controllers told them to hold in the air, without giving any reasons.

For the next 90 minutes, sources in the airline said, the flight circled at a height of 16,000ft (5,000m) over the capital.

Anticipating landing delays and accounting for the fact that air communication at heights around Kabul can be sometimes patchy, the plane was carrying extra fuel.

Air activity around Kabul airport is also often "busy and tedious", pilots say. During this time of the year, flying into the city poses an extra challenge: the winds are strong and gusty.

There were at least two other foreign airlines circling in the air above Kabul awaiting clearance to land.

The 160-seater Air India Airbus 320, commanded by Captain Aditya Chopra, finally landed around 15:30 Kabul time.

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Usually it took between 105 and 120 minutes to fly from Delhi to Kabul; on Sunday afternoon it had taken three and a half hours.

Some passengers on the plane recounted that they could "gauge the tension on the ground", but it was not clear what it was all about.

There were soldiers skirting the runways. There was also a roar of air activity: C-17 Globemaster military transport aircraft and Chinook helicopters were flying in and out.

And they saw civilian airplanes belonging to Pakistan and Qatar parked on the tarmac.

Taliban fighters outside the international airport in Kabul on Sunday

"We heard that airport workers were sheltering at the airport, and there was a big rush of people trying to enter the airport," a passenger on the Air India flight said.

After the flight landed, the crew stayed in the cockpit as is the protocol in Kabul.

After waiting more than an hour and a half on the tarmac, the Air India plane took off with 129 passengers. Among them were some Afghan officials, at least two MPs and a senior advisor to the former president. A number of others possibly missed the flight because they were caught in traffic jams in Kabul.

"I have never seen the plight of citizens of a country so desperate to leave their land. When they walked into the plane, you could see that desperation in their eyes," one passenger said.

The majority of passengers on the flight were Afghans, escaping their country. There were also several returning Indian workers.

By the evening, there was a desperate rush of Afghans to the Kabul airport to catch a flight out of the country - videos emerged of pell-mell crowds of men, women and children inside the airport and milling on the tarmac. Major airlines were rerouting their flights to avoid flying over Afghanistan.

On Monday morning videos emerged of a rush of passengers scrambling for an evacuation flight out of Kabul.

In 1999, an Indian Airlines - which later merged with Air India - jet was hijacked en route to Delhi from Kathmandu with 180 people on board. It was flown to Kandahar in Afghanistan, from where the hijackers negotiated the release of militants fighting in Kashmir. India released three Kashmiri militants in exchange for the passengers. None of the five armed hijackers were caught.

Air India has been operating regular flights to Kabul after the war ended, but everything is uncertain now. A spokesperson said there was a scheduled commercial flight to Kabul on Monday afternoon.

"But if the airspace is closed, we won't be able to operate."