AN ACR FLC OF AN LGT DECIDES; AFTER GETTING AIRBORNE; THAT THEIR CURRENT FUEL LOAD IS INSUFFICIENT TO SAFELY FLY TO THEIR DEST AND HAVE ADEQUATE RESERVE FUEL. THEY RETURN TO THEIR DEP ARPT.

Narrative

SCHEDULED DEP FROM MSY WAS XA15Z. AFTER LONG DELAY DUE TO GND STOP AT ORD DUE TO TSTM; WE DEPARTED MSY AT XC07Z. DURING TAXI OUT; ATC GAVE US AN AMENDED CLRNC. THE ORIGINAL CLRNC WAS FOR A FLT OF 1 HR 52 MINS WITH 39000 LBS OF FUEL REQUIRED. THE RERTE WAS DIRECT AEX DIRECT DFW DIRECT LBL DIRECT LAA DIRECT GLD DIRECT OBH DIRECT MCW DIRECT GRB DIRECT PMM DIRECT ORD. ATC ASSURED US THAT THIS RTE WAS FOR A 'TECHNICALITY' AND A MORE DIRECT ROUTING COULD BE ATTAINED ONCE AIRBORNE. WITH 150 ANXIOUS PAX WANTING TO GET TO ORD THE CREW WAS IN A 'GO MODE' AFTER AIRBORNE. THE CREW BEGAN TO COORDINATE FOR MORE DIRECT ROUTING DIRECT TUL DIRECT MCW AS REQUESTED AND OBTAINED. A FLT PLAN FROM DISPATCH WAS OBTAINED WHICH SHOWED A LNDG FUEL AT ORD OF 8000 LBS. WITH AN INTENSE LINE OF TSTMS BTWN TUL AND ORD THE CAPT AND CREW DECIDED THAT 8000 LBS WAS NOT SUFFICIENT FUEL FOR THE REMAINING FLT. THE CREW DECIDED TO RETURN TO MSY WHERE CUSTOMER SVC WAS AVAILABLE FOR THE 147 PAX. LESSONS LEARNED: 1) FATIGUE AND THE 'GO MODE' LED THE CREW 'DOWN THE PATH' OF LETTING THE CTLR MAKE US THINK THAT THE RERTE WAS DUE TO ATC FLOW INTO ORD INSTEAD OF A WX RERTE; AS WAS ACTUALLY THE CASE. 2) THE CREW SHOULD HAVE CONTACTED DISPATCH PRIOR TO TKOF INSTEAD OF AFTER TKOF; WHEN THE RERTE WAS ISSUED TO DETERMINE A MORE APPROPRIATE RTE OF FLT WITH OUR FUEL LOAD.