ACR X TCASII TA HAD CONFLICT WITH A FLT OF MIL FGTS. SEE AND AVOID CONCEPT.

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ACR X DURING DSCNT ON STAR INTO RDU; I ENCOUNTERED A FLT OF F-15'S. I WAS CLRED TO CROSS ARGAL AT 10000 FT AND 250 KIAS. RDU APCH CALLED OUT A FLT OF 3 F-15'S AT 11 O'CLOCK AND 4 MI; NEBOUND; LAST RPTED ALT WAS 11500 FT; AND SUGGESTED LEVELING AT 12000 FT UNTIL PASSING THE ACFT. INITIALLY; NO TFC WAS DEPICTED ON THE TCASII. A TARGET WAS THEN DISPLAYED AT 11:30 AND 3 MI. I SOON SPOTTED THE F-15 FLT LEADER; WHO APPEARED TO BE AT 11500 FT; BASED ON TCASII ALT INFO. WE CONTINUED DSNDING OUT OF 13000 FT AND NOTICED A SECOND F-15 AT ABOUT 13500 FT; 11:30 O'CLOCK POS AND 1/2 MI. THE THIRD F-15 WAS NOT SPOTTED VISUALLY. ONLY THE LEAD F-15 WAS OPERATING HIS XPONDER; SO HE WAS THE ONLY TARGET DISPLAYED ON TCASII. NO EVASIVE ACTION WAS NEEDED SINCE I WAS DSNDING WHEN I SPOTTED THE SECOND F-15; BUT WE GOT CLOSER TO THE ACFT THAN WAS APPROPRIATE. THE CTLR STATED THAT THE FLT OF 3 WAS DESIGNATED AS MIL Y AND THEY WERE ENRTE TO VR 5415. TO MINIMIZE THE CHANCES FOR A MIDAIR COLLISION I DON'T BELIEVE THE F-15'S SHOULD OPERATE VFR AND IF THE FORMATION IS NOT TIGHT; ALL ACFT IN THE FLT SHOULD OPERATE THEIR XPONDERS. IF THE GEOMETRY OF THIS INCIDENT WAS SLIGHTLY DIFFERENT; AN RA FROM THE TCASII ON THE FLT LEADER COULD HAVE CAUSED US TO CLB INTO THE WINGMAN. I DON'T BELIEVE THAT THIS IS AN ISOLATED INCIDENT; AND THAT PROCEDURAL CHANGES ARE NECESSARY.