Hey Harrymann. This seems highly relevant to me, I have also been searching such cases to validate my little speed computations (as a function of the thrust, angle of dscent, altitude, etc...). On the DC-8 cases (reaching Mach 1.012 around FL410 starting over FL500 and Mach 0.82), it would require 3 mn of a 5° controlled dive but I haven't found this historical details:
