A B757 DEPARTING DSM; IA; HAS A CHANGE OF DEST JUST AS IT BEGINS TO TAXI. DISPATCH DOES NOT GET THE NEW DEST TO THE FLC UNTIL AFTER IT IS AIRBORNE. FLC WAS CONFUSED OVER PROPER DEST AS COM OF THE CHANGE WAS NOT EXTENDED IN AN UNDERSTANDABLE WAY TO THE FLC.

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AN ALL CARGO ACR FLT WAS SCHEDULED TO DEPART DSM AT AB00Z FOR MHT. COMPANY ADVISED THE DISPATCHER THE FLT WAS GOING TO BE REROUTED TO BDL DUE EXTRA BDL PAYLOAD. THE STATION WAS GOING TO LOAD THE ADDITIONAL PAYLOAD. (GOING IN THE FUTURE SENSE.) THE DISPATCHER WAS ADVISED APPROX AA57Z. THE CREW WAS NOTIFIED VIA ACARS OF THE CHANGE. CREW ADVISED APPROX AA59Z. ZMP FLT DATA CONTACTED AND THE DSM- MHT CLRNC CANCELED AND A NEW FLT PLAN WAS FILED DSM-BDL. A NEW DISPATCH RELEASE WAS PREPARED AND XMITTED TO THE STATION. AT AB01Z THE ACFT TAXIED AND TOOK OFF. THE CREW DID NOT REVIEW THE ACARS MESSAGE SINCE IT HAD BEEN XMITTED DURING A CRITICAL PHASE OF FLT. OUT OF ABOUT 3000 FT THE CREW DID REVIEW THE ACARS MESSAGE AFTER BEING QUERIED BY ATC WHO HAD RECEIVED A CANCELLATION FOR THE MHT CLRNC AND A NEW STRIP FILED TO BDL. THE CREW WAS STILL PLANNING TO FLY TO MHT NOT KNOWING OF THE COMPANY'S REQUEST. THE MHT CLRNC WAS REACTIVATED AND BDL CANCELED. THE FLT WAS APCHING ZAU AIRSPACE WHO NOW HAD A STRIP SHOWING BDL AND A ROUTING TO THAT DEST. ZAU REFUSED A HDOF UNTIL A DEST AND RTE WAS DETERMINED. THE ACFT WAS FLYING AT APPROX 8000 FT IN DSM'S AIRSPACE AND INTERFERING WITH THEIR ARRS. THE CREW CONTACTED THE DISPATCHER BY VOICE; THE CONFUSION OVER THE DEST RESOLVED AND THE ORIGINAL FLT DISPATCH RELEASE AMENDED. THIS BECOMES A CASE OF SEVERAL MISCOMS. THE INFO FROM THE COMPANY TO THE DISPATCHER IMPLIED A REROUTING OF THE ACFT WAS GOING TO OCCUR IN THE NEAR FUTURE. IN FACT THE EXCESS PAYLOAD HAD ALREADY BEEN BOARDED AND THE FLT WAS READY TO DEPART. THE STATION DID NOT ADVISE THE CREW OF ANY CHANGE IN PLAN. THE DISPATCHER WOULD NOT HAVE CANCELED A CLRNC AND REFILED KNOWING THE FLT HAD TAXIED. BY REFILING A NEW CLRNC THIS EXACERBATED THE PROB.