I've found most offences take place towards the end of a night shift, and as the size of aircraft increases, so does the likelihood of non-conformance. Airlines must know we've got Mode S. When I'm really busy at 5:30am, I'd rather not have to get into conversations as to why someone isn't doing the speed I told them to. 2 Union Jack coloured 747s were in trail into LTMA by about 9nm. The back one decided to fly faster than I told them to, got to 6nm behind and the reported encountering wake from his colleague ahead of him
Recently, a European operator of solely B738s with continuous 'when ready' descent was rapidly eroding any spacing I had created between him and his colleague ahead by flying at 50kts quicker than instructed for the entire descent.
I've had a conversation with a red and white 747 on the RT before about speeds, the conversation going along the lines of:
-Reduce to M.80
-Is that the fastest we can go?
-Affirm
-But we can fly much faster...
-Yes, but you'd need to do M2.0+ to overtake the 767 ahead of you and create the required spacing I need before handing you over to the next sector.
@ N90-EWR
I'd like to add to that crews who dive down at the start of their descent rather than following a normal profile, then being significantly lower than the a/c 10nm behind and subsequently slow down much more quickly screwing up the spacing.