B737-500 CREW HAD TRACK DEV IN ZAU CLASS A AIRSPACE.

Narrative

OUR ORIGINAL DISPATCH RELEASE FILED FLT PLAN WAS 'RBS J19 STL RZC J105 MLC CUE ACT BLEWE 1 AUS.' OUR FILED ALT WAS FL350. WHEN WE RECEIVED OUR PDC OVER ACARS; WE NOTICED THE REQUESTED ALT FL280. WE THEN CHKED OUR RELEASE AND SAW THAT WE WERE NOW ON RELEASE 3. OUR DISPATCHER SENT US THE NEW RELEASE WITH NO EXPLANATION. WE DID; HOWEVER; NOTICE FL280 AND ADDITIONAL FUEL. OUR FMS HAD ALREADY BEEN PROGRAMMED AND VERIFIED USING THE ORIGINAL RELEASE. THE PDC SHOWED NO AMENDED RTE. AS WE PASSED RBS AND TURNED DOWN J19; ATC TOLD US WE SHOULD BE FLYING J71. UPON; LOOKING AT THE PDC; WRE REALIZED RELEASE 3 WAS FOR A NEW FILED RTE. WE PROMPTLY TURNED AND PROCEEDED DOWN J71 TO ENL AND MEM. THE NEW RTE WAS ON THE PDC; BUT WE OVERLOOKED IT NOT REALIZING IT BEING THE REASON FOR RELEASE 3. DISPATCH SHOULD HAVE PROVIDED US A NEW RELEASE EARLY WITH THE REVISION WHY (IE; NEW RTE). WE SHOULD HAVE BEEN MORE DILIGENT IN CHKING THE PDC AGAINST OUR NEW RELEASE. WE WERE SOMEWHAT RUSHED DUE TO LATE INBOUND ACFT AND CAPT DOING IOE IN INBOUND ACFT (DOING EXTENSIVE DEBRIEF).