FLC OF ACR LTT ACFT OPERATED THE ACFT WHEN IT WAS NOT AIRWORTHY DUE TO MISINTERPRETATION OF THE 'MEL' DEFERRED ITEM WRITE-UPS.

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ALTHOUGH WE PERFORMED ALL THE REQUIRED PREFLT FUNCTIONS; I DID NOT GET A CHANCE TO CLOSELY INSPECT THE PREVIOUS LOGBOOK ENTRIES. I DID; HOWEVER; NOTE THAT THE PROPER MAINT AND FLT RELEASES WERE ON BOARD; AS WELL AS ALL OTHER REQUIRED PAPERWORK. I ALSO NOTICED THAT THE L HAND BLEED AIR SHUTOFF VALVE AND THE L HAND ENVIR OFF ANNUNCIATOR LIGHT WERE BOTH PLACARDED UNDER MEL PROVISIONS. THE SIGN-OFFS AND DEFERRALS FOR BOTH THESE ITEMS WERE VALID; BUT WE FAILED TO NOTICE THAT MAINT HAD ENTERED A WRITE-UP TO HAVE THE AIRPLANE FERRIED THE PREVIOUS NIGHT TO REPAIR THIS SYS. THIS WAS APPARENTLY PLANNED BECAUSE OF THE MEL PROVISION FOR INOP BLEED VALVES WHICH REQUIRES THE ENVIR OFF ANNUNCIATOR TO BE USED AS PART OF THE VERIFICATION FOR SYS SHUTOFF. SINCE THE LIGHT WOULD NOT ILLUMINATE; THE 2 SYS FOR THE SAME SIDE CANNOT BE JOINTLY PLACED ON THE MEL. THIS DISCREPANCY WAS OVERLOOKED BY SEVERAL PEOPLE AS THE MEL WRITE-UPS WERE AUTHORIZED AND THE FERRY AUTHORIZATION WAS LEFT WITHOUT SIGN-OFF. IT WAS NOT UNTIL THE NEXT CREW (3 FLTS LATER) MORE CLOSELY INSPECTED THE LOGBOOK THAT THE IMPROPER ENTRIES WERE DISCOVERED. EVEN THEN; THERE WAS CONFUSION BTWN FLCS; DISPATCH; MAINT; AND EVEN AN FAA INSPECTOR IN BOSTON AS TO WHAT THE PROPER ENTRIES SHOULD HAVE BEEN. THE MELS SHOULD NEVER HAVE BEEN AUTHORIZED AND THE FERRY FOR MAINT SHOULD HAVE BEEN SIGNED OFF. ALTHOUGH NO SAFETY HAZARD EXISTED; A DEFINITE COM BREAKDOWN DID OCCUR RESULTING IN EVERYONE; INCLUDING US; BELIEVING THE ACFT HAD NO OPEN WRITE-UPS SINCE THE NORMAL ACCEPTANCE PROCS WERE FOLLOWED. TO AVOID FUTURE OCCURRENCES OF THIS NATURE; I SUGGEST THE FOLLOWING STEPS: ACCEPTANCE CHKLIST INCLUDE THAT BOTH CREW MEMBERS SIGN MAINT RELEASES INDICATING THEY HAVE REVIEWED DISCREPANCIES. MEL IMPROVED TO INCLUDE EASY-ACCESS XREFING FOR SYS THAT WILL AFFECT EACH OTHER.