DELAYS AND REROUTES AFTER LEAVING THE GATE RESULT IN MINIMUM FUEL DECLARATION AT DESTINATION BY A320 FLT CREW.

Narrative

WE WERE RELEASED FROM ORD WITH 26.7 FUEL ON BOARD; TKOF MINIMUM FUEL 25.9; BURN TO LAS 19.9. ON TAXI OUT AT ORD; GND TOLD US TO BE READY FOR A RERTE. AFTER EXTENDED TAXI DELAY; WE HAD NEW RTE; REVIEWED IT WITH DISPATCHER; NEW BURN WAS 21.0. WE TOOK THE RWY WITH 26.0 ON BOARD. ENRTE; WE REQUESTED WINDS FOR OUR NEW RTE AND ESTIMATED FUEL ON BOARD AT LAS WOULD BE 4.5 WHICH WAS ACCEPTABLE. ON DSCNT INTO LAS; ZLA WANTED TO RERTE US FROM THE TYSSN ARR UP TO KSINO AND THE GRNPA ARR. WE PLUGGED THAT INFO INTO THE FLT PLAN MINUS THE DOWNWIND LEG FOR RWY 25L AND FUEL WAS NO LONGER ACCEPTABLE. WE TOLD ATC WE COULD NOT ACCEPT THAT ROUTING. THEY ASKED IF WE WERE DECLARING AN EMER. WE DECLARED MINIMUM FUEL AND PROCEEDED BASICALLY DIRECT TO THE ARPT. BECAUSE OF THIS ACTION; WE LANDED WITH 5.0 FUEL ON BOARD. IF WE WOULD HAVE COMPLETED THE RERTE; FUEL WOULD NOT HAVE BEEN ADEQUATE. OUR ORIGINAL RTE LEAVING ORD SENT US DIRECT THROUGH A LARGE AREA OF TSTMS WITH BASICALLY NO FUEL TO DEVIATE. I FEEL IN MANY SITUATIONS CARRYING MINIMUM FUEL COULD OFTEN COST MORE THAN IT SAVES. THIS EVENT HAPPENED BECAUSE AN INADEQUATE AMOUNT OF FUEL WAS PLANNED FOR THIS FLT WITH THE CIRCUMSTANCES AT THE TIME FOR THE ARPT; WHICH GETS BACKED UP BECAUSE OF CONGESTION. THIS APPLIES TO ORD AND LAS. LOAD WITH ACFT WITH ADEQUATE FUEL NOT ONLY FOR WX BUT FOR TFC CONGESTION; WHICH IS USUALLY MORE OF A FACTOR IN DELAYS. PLANNING MINIMUM FUEL NOT OFTEN EQUALS LEAST COST. DIVERSIONS ARE ALWAYS MORE EXPENSIVE.