Originally Posted by
chevvron
I've had 2 DC8s at M=0.82 about a mile apart at FL350.
They were handed over to me one on top of the other at 330 and 350, same route and destination, different airlines; the lower one asked for FL370 so with both pilot's consent, I cleared him for a VMC climbthrough.
Can't do it now in the UK, FL100 or below only.