THE FLC NOTICED THEY WERE 10 MI OFF COURSE AS THEY NAVED BY THEIR FLAWED OMEGA. THE FLC TURNED 40 DEGS TO GET BACK ON COURSE. ATC HAD A TFC CONFLICT BECAUSE OF THIS EVENT.

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PROCEEDING TO NASHVILLE VOR VIA THE OMEGA. THE OMEGA APPEARED TO BE ALMOST 10 MI OFF COURSE NW OF THE VOR. THE CAPT WAS FLYING THE ACFT AND BEGAN A TURN FROM A 070 DEG HDG TO APPROX A 110 DEG HDG TO POS THE ACFT OVER THE VOR FOR A POS UPDATE. AS THE ACFT ENTERED THE 'CONE' OVER THE VOR; THE CAPT BEGAN A TURN FOR THE 070 DEG RADIAL OUT OF BNA. PASSING APPROX 100 DEGS; ATC CALLED US AND TOLD US TO TURN 40 DEGS TO THE L FOR TFC. WE ACKNOWLEDGED THE TURN INSTRUCTIONS AT ABOUT 085-090 DEGS. THEN ATC ASKED US WHAT OUR HDG WAS; I REPLIED THAT WE WERE MAKING A COURSE CORRECTION FOR OUR OMEGA BUT THAT WE WERE TURNING BACK TOWARDS COURSE WHEN HE CALLED WITH THE VECTOR. ATC THEN CALLED TFC AND TOLD THEM TO DSND IMMEDIATELY TO FL310 AND TO TURN TO A HDG OF 210 DEGS. ATC THEN INSTRUCTED US TO TURN IMMEDIATELY TO A 225 DEG HDG. WE BEGAN THE TURN; SAW THE ACR X ACFT ON THE TCASII APPROX 10 MI IN FRONT OF US IN A DSCNT TO FL310. THE TCASII ADVISED US OF THE TFC; AT THE SAME TIME ACR X SAID THEY HAD US VISUALLY. ATC THEN CLRED ACR X TO RESUME NAV; AND I ASKED IF WE COULD ALSO RETURN TO COURSE; WHICH ATC APPROVED. LOTS OF HEADS UP LESSONS WERE LEARNED FROM THIS EVENT. ATC COORD AND EXPECTATIONS OF ATC VERSUS AIRCREWS IS ESSENTIAL.