Now that a COVID-19 vaccine is finally in sight, governments, employers, schools, and service providers are debating whether or not to mandate compulsory jabs. One airline carrier is taking a stand on the matter.

On Thursday, Alan Joyce, the CEO of Australia’s Qantas Airways, said that Qantas will require passengers to prove that they’ve been vaccinated for COVID-19 in order to board international flights.

“Australia’s success at virtually eliminating COVID means we’ll need a vaccine for international travel to restart properly,” Joyce said on a call with investors on Thursday. “We have a duty of care to our people and to our passengers, and once a safe and effective vaccine becomes readily available, it will be a requirement.”

Joyce first suggested that his airline was looking into the policy in late November. Qantas appears to be alone among global airlines in mandating that passengers be vaccinated.

A Singapore Airlines spokesperson told Fortune it would “work closely with all relevant government authorities and be guided by the advice of health professionals.” The spokesperson also said that the recent vaccine announcements “provide hope” that rolling out the vaccines will spur a recovery in air travel.

AirAsia, the Malaysian low-cost airliner, told CNN in November that it would only review making vaccines mandatory once immunizations become widely available. Air New Zealand also told CNN at the time that “ultimately, it’s up to governments to determine when and how it is safe to reopen borders, and we continue to work closely with authorities on this.”

Asian airlines Cathay Pacific and Taiwan’s Eva Airways as well as U.S. carriers Delta, United Airlines, and American Airlines did not immediately return Fortune‘s request for comment on whether they will mandate passenger vaccinations.

Airlines are grappling with the question as the world awaits the start of mass vaccination campaigns. Currently, three vaccine makers have posted promising clinical data from Phase III trials. The U.K. became the first country in the world this week to authorize a science-backed vaccine for high-risk groups when it gave Pfizer’s vaccine the green light. The U.K. will start distributing the doses next week.

Qantas’s vaccine requirement largely reflects the Australian government’s stance on the matter.

In November, Australia’s Health Minister Greg Hunt said that the Australian government may require travelers to provide “proof of vaccination” in order to enter its borders. In August, Australian Prime Minister Scott Morrison suggested on a radio show that he would make a vaccine compulsory for all Australians, though he later walked back the comments.

Australia’s impulse to mandate vaccines illustrates how risk-averse it is about COVID-19, the disease it’s worked so hard to contain.

Australia has recorded just a handful of new COVID-19 infections per day after months of strict lockdowns and rigid border requirements. Amid the pandemic, Australia has largely banned its own citizens from leaving the country and imposed weekly caps on how many Australians can return home.

Industry experts argue that proving travelers are vaccinated—perhaps with an immunization passport of sorts—is unrealistic on a global scale given the looming production and distribution complexities of vaccinating the world’s population.

The International Air Transport Association (IATA), the leading trade association for global airliners, said in November that it doesn’t expect vaccines to be widely available until the middle of 2021. In the meantime, governments should work with airlines to open up borders and replace mandatory quarantine periods for international travelers with more testing, medical adviser David Powell said at an IATA meeting in November.

The travel industry’s early optimism about so-called travel bubbles has faded with the latest failure: the delay of a much-hyped Hong Kong–Singapore route because of a new COVID-19 outbreak in Hong Kong.

On Thursday, Qantas’s Joyce said the stalled bubble proved vaccines are the best hope for returning global travel back to normal.

“The potential for vaccines to be rolled out maybe faster than the bubbles happening is probably real at this stage,” he said.