The world's airlines are stepping up efforts to start delivering COVID-19 vaccines as health regulators signal further approvals are likely in coming weeks. 

Experts say it will take the equivalent of 8,000 jumbo jets to safely distribute billions of doses of vaccines to the world's population. Air freight companies are adjusting schedules to meet the growing demand, and some airlines are redeploying passenger aircraft to help add capacity to their cargo fleets. 

Germany's Lufthansa Cargo said it had spent months planning its routes and delivery schedules to accommodate the arrival of the new vaccines. The company already houses a specialist division dedicated to delivering pharmaceutical goods. 

"Luckily we are working according to processes that are already fixed and everybody is trained to handle and store cargo shipments. We are proud to be part of this transportation chain for COVID-19 vaccines. The processes are already running smooth so I'm quite sure that everything will work well," said Karin Krestan, head of Lufthansa Cargo's Pharma Hub. 

Several leading vaccine candidates need to be stored at sub-zero temperatures. BioNTech and Pfizer's vaccine needs to be kept at -70 degrees Celsius during transportation. 

To achieve this, air freight companies like Lufthansa Cargo use specialised containers which are temperature-controlled using dry ice. Shipments are also scheduled to ensure deliveries arrive with enough time to safely move the medicine from container to freezer at the destination. 

For many working on Lufthansa's distribution efforts, there's an added sense of national pride. The BioNTech vaccine was developed not far from the airline's Frankfurt hub, meaning a vaccine developed in Germany will now largely be distributed to the world aboard German aircraft. 

"We're all very excited to see what was happening and what are our main destination is going to be. If it's the whole world, then it's got to be transported to every country and we have a lot of freighters, but it's actually pretty tough work to cover the whole world with the vaccine. We will see how this will be handled," said Denis Hoffmann, from Lufthansa Cargo's Cool Center. 

The distribution of the COVID-19 vaccine is set to be one of the largest airlift operations in human history. 

To help meet demand, Lufthansa is increasing cargo capacity. The carrier already has a fleet of 17 freighters but it is also repositioning passenger aircraft to help speed up deliveries. It recently removed an Airbus A340 passenger jet from its winter schedule, to be used to fly cargo exclusively between China and Germany.