It would be interesting to know what rotation this crew in CUN had done, they sometimes go via Roatan in Honduras and then on to Cancun. I did this a few weeks back, it was 12hrs 50mins flying time (about 13hrs 15mins block time)to RTB, one hour on the ground and then another hour on to CUN (total duty time was 18hrs 30mins). I was in no fit state to fly an aircraft by the time it came to land in CUN and in fact I had a bit of a fright on the approach into CUN not from my lack of flying skills but from my state of total fatigue and slowness to react. For a duty time of this length they give you a third crew member but with the flight deck jump seat usually the only place to rest you do not get much in the way of rest at all. . .Italian duty times of 24 hours with 17 hours flying time (with a three man crew) make this duty legal but would the passengers really fly if they knew what state the guy at the front was in. I seriously frightened myself, I am glad that I am leaving and do not have to do it again.