NEW DELHI - The arrival of coronavirus-infected passengers on flights from India remains a concern for other countries at a time when the Indian government is attempting to augment international air passenger traffic through bilateral travel bubbles.

On Tuesday (Sept 22), Saudi Arabia, a key destination for Indian migrant workers, suspended air travel to and from India amid concerns of potential imported cases.

This development comes after two airlines - Air India and Air India Express - were handed temporary bans last week by the authorities in Hong Kong and Dubai for flying in Covid-19 positive passengers to these two cities.

Hong Kong barred Air India for a fortnight until Oct 3, after one of its flights to the city on Sept 18 carried six infected passengers.

The Hong Kong government strengthened regulations this month stipulating that any airline that carries five or more Covid-19 passengers on a flight would be banned from flying to the city, said a report in South China Morning Post. Such a ban would also apply if it operates two consecutive flights with three or more diagnosed passengers.

This is the second time the authorities in Hong Kong have banned Air India. A similar two-week suspension order was handed out to the airline last month, after it flew 14 Covid-19 positive passengers to the city on Aug 11.

Prior to this, Air India Express was issued a 15-day ban by the Dubai Civil Aviation Authority on Sept 17. This was because the airline's ground handling agents failed to prevent two passengers with positive Covid-19 reports from boarding flights to Dubai - one from Delhi on Aug 28 and the other from Jaipur on Sept 4.

The suspension order was, however, revoked on Sept 18 following an apology and assurance of better pre-boarding checks, an Air India Express spokesman told The Straits Times.

India has recorded more than 5.6 million confirmed Covid-19 cases but serological surveys indicate a far greater spread of the infection that is yet to show any convincing sign of having peaked. As a result, several countries now require visitors flying in from India to produce a polymerase chain reaction (PCR) test carried out within 72 hours before departure certifying them to be negative.

Beginning Sept 17, Singapore introduced this requirement for travellers from India who are not Singapore citizens or permanent residents. This is on top of the existing requirement of a 14-day stay-home notice (SHN) at dedicated facilities and a negative Covid-19 test before the end of their isolation. Between Sept 17 and 21, nearly two-thirds of Singapore's imported cases had visited India.

The city-state further tightened its restrictions this week. Starting on Wednesday (Sept 23), all travellers - including Singapore citizens and permanent residents - with a travel history to India within the last 14 days before coming to Singapore will have to take a serology test. The test detects the presence of antibodies and can show if the person might have been infected.

Hong Kong also requires visitors from India to have a negative "nucleic acid test" report conducted 72 hours prior to departure, along with proof that the test was conducted in a laboratory recognised by the local government. Travellers also must have a hotel room reservation in Hong Kong for not less than 14 days starting on the day of arrival.

An Air India spokesman told The Straits Times that the airline has been "strictly adhering" to all passenger screening requirements for flights to international destinations and that, wherever applicable, only passengers with Covid-negative reports are allowed on board.

He said passengers are tested again for Covid-19 after landing in Hong Kong and the results "may vary from the reports of tests conducted 72 hours before taking the flight".

"Hence, Air India cannot be held responsible for any lacunae on the issue of passenger test reports," he added.

The ban led to the cancellation of an Air India flight to Hong Kong scheduled for Sept 21.

The Indian government has been setting up travel bubbles with other countries to allow smoother international air passenger traffic. It has such an arrangement with 13 countries. Regular scheduled commercial flights have been suspended in India since March 25.

With limited options to fly abroad, there has been a demand for international chartered flights to lesser-served destinations, including Hong Kong.

Mr Pradeep Sharma, the director of Kolkata-based Agwani Travels, said his agency has organised two such flights to Hong Kong with Singapore Airlines. It is working on another three flights next month to the city.

"The kind of documentation that Hong Kong requires is very challenging for anybody to procure within 72 hours of departure. Often the final approval for a flight comes just 48 hours before departure," he said.

Kuwait also forbids commercial flights to and from "high-risk" countries such as India, forcing many Indian migrant workers to fly to the UAE and spend additional money on a 14-day quarantine there before heading to Kuwait.