Flight Crew Last 90 Days 183
Confusion; Communication Breakdown
ATC Issue All Types; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert
Procedure
Prior to arrival into LAS; we were assigned 280 knots.  At some time during the arrival; we were cleared to descend via the SUNST 3. We set the VNAV and verified that the aircraft crossed FUZZY at 16;000 feet and slowed to 250 knots.  A short time later; ATC queried us about our airspeed.  We replied that we had slowed to 250 to comply with the arrival.  He stated that he thought that we had been assigned 280 knots.  We replied that we had; but that our understanding was that speeds on the arrival superseded previously assigned speeds.  At no time prior did the Center Controller ever say anything along the lines of 'DISREGARD SPEEDS AT FUZZY' or similar.We believe that we were correct in our interpretation of ATC directives as they were given to us; even if it wasn't what the Controller intended.The Approach Controller stated that it wasn't a problem; he was just expecting us to be doing 280 knots and wanted to make sure we were all on the same page.
[Report narrative contained no additional information.]
An air carrier flight crew slowed to meet the charted RNAV arrival speed constraint after being cleared to 'descend via' the arrival. ATC advised that they were expected to maintain the previously assigned speed.