CPR ACFT ON LOC BC APCH SIGHTS DN LINES UP WITH WRONG ARPT.

Narrative

SEA APCH HAD VECTORED US TO INTERCEPT THE LOC BC RWY 31 AT BFI; GIVING US A HDG THAT LINED US UP PERFECTLY WITH THE RWY AT RENTON; WA. AS WE DSNDED THROUGH THE CLOUD BASES; RENTON; WA. AS WE DSNDED THROUGH THE CLOUD BASES; RENTON CAME INTO SIGHT AND I STATED THAT I THOUGHT I HAD THE ARPT. THE CAPT CONTINUED TO FLY THE VECTOR; AND I MONITORED THE OUTSIDE. IT BECAME APPARENT THAT WE WERE TOO HIGH FOR THE RWY; SO THE CAPT BEGAN A STEEP DSCNT; FLEW THROUGH THE BFI LOC; AND BUSTED THE ALT MINIMUMS FOR THAT SEGMENT OF THE APCH. ABOUT THE TIME THAT WE BOTH DECIDED THINGS WERE DEFINITELY WRONG; BFI TWR CALLED US TO ALERT US TO THE FACT THAT WE WERE HEADED FOR THE WRONG ARPT. WE DID A 270 DEG TURN; RE-ESTABLISHED ON THE BFI LOC (WHICH WE HAD BOTH MISSED DURING OUR ATTEMPT TO MAKE RENTON) AND LANDED WITHOUT INCIDENT -- AND WITH GREAT EMBARRASSMENT. IT WAS A þSUCKER-PUNCH' EVENT. I HAVE BEEN TO BFI MANY TIMES AND AM FAMILIAR WITH THE ARPT. I SHOULD HAVE NEVER CALLED THE ARPT IN SIGHT WITHOUT VERIFICATION. THE CAPT SHOULD NOT HAVE GONE FOR THE RWY WITHOUT LOC VERIFICATION. I SHOULD HAVE BACKED HIM UP BETTER BY NOT FOCUSING SO MUCH ON THE OUTSIDE ENVIRONMENT AS TO FORGET MY DUTIES INSIDE THE COCKPIT.