A XING RESTR IS NOT MET BECAUSE OF THE ALTIMETER NOT BEING SET TO QNH DURING DSCNT BELOW FL180.

Narrative

WHILE PASSING THROUGH FL180; RECEIVED A HDOF FROM ZFW TO REGIONAL APCH. HAD BEEN PREVIOUSLY ISSUED A CLRNC TO CROSS HOWDY INTXN AT 11000 FT. MY FO WAS THE PF. I (THE CAPT) WAS THE PNF. SINCE FL180 WAS THE TRANSITION ALT; ALTIMETERS SHOULD HAVE BEEN SWITCHED OVER FROM 29.92 TO 30.42. AS A RESULT OF THIS ACTION NOT BEING ACCOMPLISHED; OUR LEVELOFF WAS 500 FT HIGHER THAN SHOULD HAVE BEEN. WHEN APCH ASKED ABOUT OUR ALT; I REALIZED THIS FACT. I WAS SOMEWHAT DISMAYED AT MY OVERSIGHT OF THIS ALL TOO IMPORTANT CHKLIST ITEM; AND WONDERED WHAT CONTRIBUTED TO THIS. I THINK I KNOW WHAT HAPPENED. WHEN THE HDOF CAME FROM ZFW AT FL180; I THOUGHT THIS WAS AN EARLY HDOF. I WONDERED IF I WERE TO REQUEST THE W SIDE FOR PARKING; WOULD I GET IT? I LET AN EVENT THAT OCCURRED AT A TIME THAT IT WAS UNEXPECTED; AND THOUGHTS OF POST-LNDG EVENTS BASICALLY OVERRIDE WHAT SHOULD NORMALLY TAKE PLACE. ADDITIONALLY; LATELY; I HAVE BEEN GOING THE EXTRA MI TO CONSERVE FUEL AS WELL AS ACHIEVE EARLY IF NOT ON-TIME ARRS. I SHOULD RE-DOUBLE MY EFFORTS TO ENSURE THAT THESE EXTRA EFFORTS NOT REPLACE NORMAL CHKLIST DISCIPLINE.