Originally Posted by
Fortissimo
As for whether it was a civil or military flight (question from atakacs), most nations treat the operation of aircraft designed for military purposes as being military in nature, regardless of the status of the crew, because the aircraft are not designed or built to the standards that would apply to a civilian aircraft. It would be for Spain to decide on publication of the investigation report for a military accident that happened on its turf, not Airbus.
In the US, military transports not yet delivered to the military customer (via DD250) are assigned a temporary FAA "N" registration and operated under FAA "Experimental" rules. Every KC-46 and C-17 that has flown was so registered prior to DD250. Indeed there are four KC-46 tankers and one C-17 stored here in San Antonio awaiting delivery to the military customer. Each has a temporary "N" number on the tail.
Separately, both the A400 and KC-46 are initially civilly certified. On the KC-46 many mods have a civil STC (Supplemental Type Certificate) and some mods have an MTC (Military Type Certificate.) But the basic airframe is civilly certified.