A DSNDING B767-300 OVERSHOT ITS ASSIGNED ALT.

Narrative

I WAS THE RELIEF PLT; TALKING TO OUR RAMP CTL AGENT. ATHENS CLRED US DOWN TO FL170. CAPT PROBABLY READ BACK FL170; BUT PF; THE FO; SET FL160. AT FL165 THE CAPT NOTICED US DSNDING TO FL160; AND MENTIONED IT TO THE FO. HE RESPONDED THAT WE WERE CLRED TO FL160. CAPT SAID GO BACK UP. FO RESPONDED 'IT'S TOO LATE NOW.' CAPT THEN QUERIED ATHENS TO VERIFY CORRECT ALT; AFTER A HESITATION THEY SAID FL170. THEY THEN CLRED US TO CONTINUE DSCNT. THERE HAD BEEN NO CONFLICT WITH ANOTHER ACFT. ALL 3 PLTS IN THE ACFT MADE MISTAKES. THE CAPT DID NOT POINT AT THE ALT SET IN THE WINDOW ACCORDING TO PROCS. THE FO FLYING DID NOT SET IN THE CORRECT ALT; AND DID NOT RESPOND SATISFACTORILY TO THE CAPT'S EFFORTS TO CORRECT THE SIT. I; AS THE RELIEF PLT; ALLOWED MYSELF TO GET DISTRACTED BY ANCILLARY DUTIES SUCH AS GETTING THE ATIS AND TALKING TO THE COMPANY. FATIGUE COULD BE A FACTOR. WE WERE IN THE 9TH HR OF OUR FLT. COMPLACENCY WAS DEFINITELY A FACTOR. THE PF WAS/IS A VERY CONFIDENT PLT WHICH COULD HAVE PERHAPS CONTRIBUTED TO THE OTHERS COMPLACENCY.