SINGAPORE - Hong Kong-based student Kengie Tang, 22, has been separated from her mother and brother in Singapore for the past six months.

Ms Tang lives with her Singaporean father in Hong Kong and had booked flight tickets home for this month. "During the months leading up to my exams, I missed my family so much, I contemplated returning home, even with the quarantine in place," she said.

But her hopes were dashed when the relaunched Singapore-Hong Kong air travel bubble (ATB) allowing quarantine-free travel between both cities was delayed again after a spike in Covid-19 cases in Singapore. The travel arrangement had been slated to take off on Wednesday (May 26).

The ATB was deferred on May 17 for the second time when the seven-day moving average of unlinked community cases in Singapore increased to six.

Both cities had said the ATB would be suspended when the seven-day moving average of unlinked community cases in either city increased to more than five.

Singapore's Ministry of Transport had said the two cities would monitor the public health situation and review the new launch date of the ATB towards the end of phase two (heightened alert) of the country's reopening.

If travellers fly to Singapore without the ATB, they would have to serve 14 days' quarantine upon arrival.

Unvaccinated travellers who fly to Hong Kong without the ATB also need to serve 21 days' quarantine upon arrival, while vaccinated travellers serve a shorter 14-day quarantine.

Singaporean Lynette Chua has been hoping that she and her newborn daughter can be reunited with her husband in Hong Kong.

The ATB, originally planned to be launched on Nov 22 last year, was postponed by both cities due to the worsening Covid-19 situation in Hong Kong.

Ms Chua, who had been based in Hong Kong for the past four years, returned home last November with her Singaporean husband for the birth of their daughter in February.

Her husband, 31, who works in a bank, spent two months with their daughter before returning to Hong Kong for work in April.

To reunite her family, Ms Chua, 32, had booked flight tickets for her husband to return home next month. The family of three also booked tickets to fly to Hong Kong in July.

She said: "I'm worried that if the ATB continues to be delayed, my daughter would not be able to recognise her father.

"The long quarantine isn't good for my baby and the hotel setting isn't ideal for caring for her. The Hong Kong government had also released a list of hotels travellers can be quarantined at, and I believe most family rooms and suites have been snapped up."

Travellers from Singapore do not need to be vaccinated to fly via the ATB but have to undergo four polymerase chain reaction tests that cost around $200 each.

This delay in the ATB meant that travellers like Ms June Ang, 31, a Singaporean based in Hong Kong, would have to miss a special family occasion.

The co-founder of a financial firm had booked a flight for Friday to celebrate her mother's 60th birthday in July and attend to business here. She had also bought tickets last October for the first ATB.

Ms Ang said: "I had to adjust flight tickets seven times since October, which was a hassle, but I'm more disappointed that I have to miss my mother's birthday. We will just have to roll on, and celebrating virtually is the best we can do in such times."

The International Air Transport Association has projected that air passenger numbers would not return to 2019 levels till 2023. Air transport should grow rapidly in 2022 and 2023 as vaccination progresses, it said.

Dr Wong King Yin, a marketing lecturer at Nanyang Technological University, said the deferred Singapore-Hong Kong ATB could cause further delays in other ATBs.

She said: "If the Singapore-Hong Kong ATB is a success, other countries would be more confident to join the two cities and help the aviation and tourism industry to recover step by step by setting up more ATBs in the region."