To date three such flights have been performed, the latest one being part of the certification flight trials.
This type of operation further illustrates the capability of the new-generation A330 MRTT tanker to refuel any kind of large receiver, even wide-body aircraft like another A330 MRTT, or receiver aircraft with complex aerodynamics such as the E-3 AWACS tested in February.
It also demonstrates the capability of the aircraft as a receiver and means that the A330 MRTT is now both the largest aircraft to have refuelled an A330 MRTT and the largest to have received fuel from it.
The two aircraft used for these flight trials were the first two A330 MRTTs built for the Royal Australian Air Force.
They are being used in the final stages of the certification program due for completion in the next months.
During the flights, performed over the Gulf of Cadiz in southern Spain, fuel was passed from the refuelling aircraft's Air Refuelling Boom System (ARBS) to the receiving aircraft's Universal Aerial Refuelling Receptacle System Installation (UARRSI).
Program director Airbus Military Derivatives, Antonio Caramazana, said the buddy-buddy refuelling between tankers was a "vital enabler for even longer-range deployments".