one aircraft from an Irish based airline which operates many 737s was descending from the cruise to around FL200 at 330kts the other day!
If there's no delay, 270-290kts seems to be the norm (unless you're a turboprop!). If I'm not too busy I'll normally ask No 1 in the stream what they're planning on converting to. Anything over about 15mins delay and I'm slowing people back to 250- kts .
Even with Mode S there are still a few pilots trying their luck flying a different speed to what I've given them. So frustrating - you're on a speed for a reason.
