A300-600
Its a perfetct size freighter with the excact economical range.
If you want to buy one they are not available. Neither is the B767 freighter. There is more demand for that size aircraft than the B747.
The B747-400 starts being economical after 6 hours. Anything less is a loss of revenue.
Ive never flown thar machine. However I know that lots of companies are looking for them. UPS had Airbus to open the production line up after it was shut down and manufacture some more for them. My friends who fly it absolutely love it. Also the B4 is favorable since the other once are not available. Now the A330F will be he replacement by Airbus.
Also keep in mind that Airbus has a absolute wonderful support for their customers and operators.