A B727 CREW; DEPARTING MEM; RECEIVED; READ BACK; AND RESPONDED TO A CLB CLRNC FROM ATC; ONLY TO FIND OUT THE CLRNC WAS FOR ANOTHER ACFT.

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WHILE ROLLING ONTO THE RWY (RWY 36) AT MEM; WE (FLT ABCD) WERE GIVEN INSTRUCTIONS TO TURN TO A HDG OF 330 DEGS. OUR ASSIGNED ALT WAS 5000 FT. THE ACFT WHICH HAD JUST LIFTED OFF THE SAME RWY; WHICH WAS ALSO A B727; HAD BEEN GIVEN THE SAME HDG (330 DEGS) AND INITIAL ALT OF 5000 FT. THE FLT NUMBER FOR THAT ACFT WAS ABCE. AS I (THE CAPT) BEGAN TO LEVEL AT 5000 FT; THE FO (OPERATING THE RADIO) RESPONDED TO ZME; 'WITH OUR CALL SIGN;' A CLRNC TO CLB TO 16000 FT. I CALLED TO THE SO FOR CLB PWR AND INITIATED THE CLB. APCHING 16000 FT; ZME XMITTED FLT ABCD 'WHAT'S YOUR ALT?' THE FO REPLIED 'ABCD APCHING 6000 FT FOR 16000 FT.' ZME CAME BACK AND SAID THAT CLRNC WAS FLT ABCE. I IMMEDIATELY LEVELED AT 6000 FT. ZME THEN XMITTED TO FLT ABCE 'CLB TO 16000 FT;' AT WHICH TIME FLT ABCE REPLIED 'CLBING TO 16000 FT.' ZME THEN CALLED US FLT ABCD AND SAID 'YOU REALLY SHOULD LISTEN MORE CAREFULLY; CONTINUE YOUR CLB TO 16000 FT.' THE POINT IS THAT FLT ABCE AND FLT ABCD WERE THE SAME TYPE ACFT WITH THE SAME FLT NUMBERS (EXCEPT FOR THE LAST DIGIT BEING ONE NUMBER OFF). TAKING OFF (ONE RIGHT BEHIND THE OTHER) ON THE SAME RWY WITH IDENTICAL CLRNCS TO 5000 FT AND ON A HDG OF 330 DEGS. PERHAPS YOU CAN APPRECIATE HOW THIS WAS A SET-UP FOR ATC OR ONE OR BOTH OF THE CREWS TO MAKE A MISTAKE. THE FACT IS; MY FO RESPONDED TO THE CLB CLRNC WHEREAS THE OTHER FLT DID NOT. PLEASE NOTE: I DID FORWARD A FLT SAFETY RPT (ANONYMOUS) TO MY COMPANY WITH THE SAME INFO AND POSSIBLE FIX. THAT IS PERHAPS A LITTLE MORE THOUGHT SHOULD BE PUT INTO ISSUING FLT NUMBERS TO ACFT DEPARTING AT OR NEAR THE SAME TIME.