ARTCC RADAR CTLR ADVISES THAT A LARGE COMMUTER AIRLINE IS UTILIZING WIDELY DIVERGENT CRUISE AIRSPDS FOR THEIR ACFT IN SEARCH OF FUEL ECONOMY. RPTR FEELS THESE SPDS ARE INCONSISTENT WITH THE SMOOTH FLOW OF TFC IN THE ENRTE SECTORS.

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THIS IS NOT A SEPARATION ISSUE; YET. ACR XYZ APPARENTLY HAS A COMPANY POLICY OF FLYING 'SLOW' TO CONSERVE FUEL. THE FIRST PROBLEM WITH THIS IS THAT YOU NEVER KNOW WHAT IAS OR MACH NUMBERS THEY ARE FLYING; AND THE SECOND PROBLEM IS THAT ONE XYZ FLIGHT IS FLYING AT M.80; AND WHEN QUERIED; THE FLIGHT DIRECTLY AHEAD MAY BE AT M.68. ON THIS NIGHT; XYZ FLT WAS OPERATING IN THE ZOB HIGH ALTITUDE AIRSPACE AT FL340 ON THE CINCE6 STAR. XYZ WAS NUMBER 2 WITH A COMPANY AHEAD DOING M.84; AND 6 AIRCRAFT BEHIND. XYZ FLT WAS ASKED HIS MACH SPEED AND REPLIED M.71; WHEN REQUESTED TO INCREASE SPEED TO MAINTAIN IN-TRAIL SEPARATION; THE PILOT DECLINED; EXPLAINING THAT M.71 WAS THE COMPANY'S FILED AIRSPEED AND THE FUEL LOAD WAS PLANNED ON THAT SPEED. ANY INCREASE IN MACH NUMBER WOULD PUT THE FLIGHT IN A MINIMUM FUEL SITUATION. SUBSEQUENTLY; THE 6 AIRCRAFT FOLLOWING XYZ; INCLUDING B757S; B737; CRJS; WERE REDUCED TO M.71 (ALL FROM MUCH HIGHER MACH NUMBERS) TO MAINTAIN IN-TRAIL SPACING AND SEPARATION. ALL THIS OCCURRED OVER 200 NM FROM CVG. THE INCONSISTENT SLOW AIRSPEEDS THAT ACR XYZ FLIES ARE A BIG PROBLEM FOR CENTER CONTROLLERS; AND AN ACCIDENT WAITING TO HAPPEN. AND TO THINK CESSNA CITATIONS JUST GOT FASTER; AND NOW THIS. AT LEAST CITATIONS FLY AT KNOWN CONSISTENT SPEEDS.