The U.S. has passed a grim milestone: more than a quarter-million deaths from COVID-19.

As the numbers continue to rise here and around the globe, all eyes are on a vaccine — with encouraging news on that front.

Pfizer is now seeking approval for the emergency use of a new vaccine, and Moderna is said to be not far behind. But getting a vaccine approved, and then delivering it, are two very big — and different — challenges.

Also, with the COVID-19 vaccine, it has to get to every remote corner of the globe by airplane.

For more insights, The World's Carol Hills spoke to Glyn Hughes, the global head of cargo for the International Air Transport Association.

Carol Hills: When you think about what needs to be done in order to distribute a coronavirus vaccine worldwide, how does it stack up in terms of the scale of the operation?

Glyn Hughes: Something on the scale and magnitude required to move the vaccine, as you said, to all corners of the planet, is unprecedented for the air cargo logistics industry. The industry has been moving vaccines for a number of decades, but it's usually been on a planned basis for specific programs, in targeted countries, where all of the questions were answered well in advance of the vaccine being put into the supply chain. All of that is different on this occasion.

Of course, one of the big challenges in getting the COVID-19 vaccines to the countries that need it is the need to keep it very cold. I mean, the Pfizer COVID-19 vaccine in particular, if it's approved, will have to be stored at -70 degrees Celsius. That's nearly -100 degrees Fahrenheit. Are most airplane jets equipped to do that?

The vaccine itself, of course, will come out of the manufacturers with a significant packaging situation in place already. It will be using dry ice, thermal insulation, thermal blankets, and polystyrene inserts, so that the actual material — i.e., the vaccine — will be protected and cocooned with the material necessary to store it at that cold temperature. The challenge for the logistics industry and of course, the governments when it arrives in-country is to maintain that product at the optimum temperature throughout the supply chain. And the airlines are equipped with the capabilities to store and transport. The airport facilities are equipped again to store and actually replenish the dry ice if need be. It needs to be replenished every five or six days. But the real challenge will come when the vaccines leave the airport and effectively go into the possession of the countries which have not necessarily moved something as precious and as delicate as this in such a large-scale manner before.

In previous vaccine distribution efforts that you're aware of or have been involved in, what typically happens, especially if you're going to a middle-range-income country or poor country? Are most countries able, once the vaccine arrives, to keep it cold?

Well, that's also what's unique about this situation. The traditional planned vaccination programs, because they have been in development for several years, the vaccines that are actually used in those programs are much more stable. And they would tend to be shipped in what we would call a conventional cool supply chain, which is between 2 and 8 degrees Celsius. It's a much more attainable and safe temperature range for the vast majority, in fact, of all the countries that air cargo serves. That type of ultracold supply chain that is needed to be implemented now is something that would be unheard of in most parts of the world.

I'm trying to visualize this. Will the vaccine be traveling in the kind of airlines we're all familiar with — like Delta, United, American passenger jets?

One of the challenges that the entire logistics industry is also being faced with right now is the sheer scale of the grounding of the passenger services. Since the COVID-19 pandemic caused many travel restrictions to be implemented, it's meant that about two-thirds of the world's commercial aviation fleet is currently parked on the ground. Traditionally, air cargo moved about 50 percent of its volume in the bellies of those passenger aircraft. Vaccines are somewhat restricted because of the dry ice and other refrigerants that are a restricted article. So, they're restricted in terms of how much you can put on a plane with passengers on that plane.

But the airlines have actually done something quite unique over the last six months. Faced with unprecedented demand for PPE and other medical support equipment, the airlines actually mobilized about 2,500 of these grounded passenger aircraft for cargo-only operations. That expertise that they've built up from using passenger aircraft will be added to the fleet of dedicated cargo aircraft. But we'd also still hope that the passenger networks will start to resume during the early part of next year so that there can be three different types of planes that could be utilized: dedicated freighter aircraft, passenger aircraft — utilized for cargo-only operations — and then that third wave, which is traditional passenger aircraft, with passengers on board, and limited quantities of vaccine in the bellies.

Where will the most of the vaccines be originating? Where will the manufacturing points be? And therefore, where will the planes need to be taking off from globally?

There are traditionally four areas where vaccines get manufactured. First is North America. Second is Europe. Third is India, and fourth is China. So most of those are concentrated, obviously, in the Northern Hemisphere. So already you can anticipate quite a sizable logistical challenge from getting from just four or perhaps five main areas of production down to the 200-plus countries and territories that will ultimately need to have their population vaccinated. So I think the key aspect here is: to protect one of us, you need to protect all of us.

Finally, I'm curious — once the vaccine is approved, or several vaccines, and this kind of global airlift begins, will delivering the vaccine take precedence over passenger travel?

Because it's more of a complementary aspect, in actual fact, we would probably encourage more passenger travel to ensure that there is that global access to those 200 countries and territories. The challenge will come to making sure that the available capacity is where it's needed to be, because the last thing anybody wants is to have an order for vaccines and no capacity to move it. So the airlines have committed to keeping that or finding that available capacity. And the industry, i.e. the humanitarian sector and the pharmaceutical manufacturers, have committed to sharing the information about the packaging requirements, the storage and control requirements, and the volumes of vaccine that will actually be produced.

This interview has been edited and condensed for clarity.

This article originally appeared at The World. Follow them on Twitter.