I can state that categorically that an F6 was capable of reaching over 75K. Admittedly, he did state that both engines had flamed out, it was very quiet, and he was slowly tumbling end over end, but still.....
(In the last couple of months before they finished at BK everyone was doing high speed runs and seeing how high they could get. So, OK, if the pressurisation had gone they'd have been dead, but if you wanted to live fore ever, who'd become a Lightning pilot anyway.....)
It also gave me the opportunity to hand over a Lightning to ATC VFR in the dive arc for recovery and, as they accepted control, casually slip in he was VFR
above at FL680.
