PARIS, Nov 18 (Reuters) - Air France-KLM is among airlines gearing up for the challenge of transporting millions of doses of temperature-sensitive COVID-19 vaccines in the midst of a travel slump.

Breakthrough vaccines developed by Pfizer and Moderna have yet to win final approval, but the drugmakers, their logistics and cargo providers are not waiting for a green light to activate freight plans.

Air France-KLM, which has decades of experience shipping medicines and vaccines in temperature-controlled conditions, is preparing a test run in coming days to fly out dummy vaccine shipments, likely from KLM's Amsterdam-Schiphol hub.

The task is complicated by the conditions required by the Pfizer and Moderna shots - with respective storage temperatures of minus 80 Celsius and minus 20C.

"It's going to be a major logistics challenge," said Air France cargo chief Christophe Boucher, citing the "massive" volume of vaccines to be distributed globally.

"Another difficulty is the temperature control," Boucher said in an interview at Paris-Charles de Gaulle airport - where cargo specialists were preparing to load consignments of super-cooled rabies vaccines bound for Brazil.

The COVID-19 airlift is being planned amid a partial shutdown of global air travel. Airlines have warned that travel curbs could hamper the effort, since around 45% of global cargo typically travels in passenger plane holds.

Air France-KLM does not rule out bringing idled jets back into service for the vaccine shipments, pharma cargo manager Florent Gand said. "We have some planes currently grounded that we can use if necessary to transport the COVID-19 vaccines around the world." (Reporting by Noemie Olive and Laurence Frost; Editing by Mark Potter)