COVID-19 vaccines, the US carrier said on Monday."American’s cargo operation began conducting trial flights, in conjunction with pharmaceutical and cargo partners, from Miami to South America on its Boeing 777-200 aircraft," the carrier said in a statement.The flights simulate the conditions required for the vaccine to stress test the thermal packaging and operational handling process that will ensure it remains stable.Both the Moderna and Pfizer vaccines rely on a technology called messenger RNA that turns the body’s cells into vaccine-making factories.