There are 60 odd ex USAF KC-10's stored in the boneyard at Davis Monthan/Tuscon. They were only retired about a year ago. They've only ever been operated by the USAF, and were in service from 1979 ish. The last ones were built (tecnically funds were allocated) in 1987. The hours and cycles on these airframes will be well documented.
If I were NTSB I'd be asking the USAF if they wouldn't mind stripping the engines and pylons off a handful of them so they can inspect the parts that broke assuming the KC10 uses the same or similar parts.
Can't see them being any different tbh, the aircraft are fundamentally the same. The designers should have forseen the potential issue as the engines are mounted a fair distance forward of the main spar. To the point it's unusual.
Be interesting to see if the 737 Max will develop similar failures over time from mounting the engines forward and up from the original -300/800 design
