Narrative:

Captain was on secondary radio with company. First officer flying at FL280 with crossing clearance of FL240 at jokur. TCASII displayed an aircraft 1500 ft below at 10 O'clock position. Visual confirmation made. Several seconds later an RA directed a descent, which was executed, then a climb was commanded and executed. Aircraft initially descended to FL275. The aircraft initially seen displayed on TCASII was not idented as the conflict on the TCASII display. No other aircraft could be idented in the area. ATC was advised of the RA actions. Note: for approximately 30 seconds prior to this event, ATC was having an ongoing and continuous dialogue with a private jet that would not follow ATC instructions to remain at altitude, slow down and make a 360 degree turn.

Related reports:

Google
 

Original NASA ASRS Text

Title: A FLC RECEIVED 2 TCASII RA'S WHILE ON THE CRESO ARR TO LAS.

Narrative: CAPT WAS ON SECONDARY RADIO WITH COMPANY. FO FLYING AT FL280 WITH XING CLRNC OF FL240 AT JOKUR. TCASII DISPLAYED AN ACFT 1500 FT BELOW AT 10 O'CLOCK POS. VISUAL CONFIRMATION MADE. SEVERAL SECONDS LATER AN RA DIRECTED A DSCNT, WHICH WAS EXECUTED, THEN A CLB WAS COMMANDED AND EXECUTED. ACFT INITIALLY DSNDED TO FL275. THE ACFT INITIALLY SEEN DISPLAYED ON TCASII WAS NOT IDENTED AS THE CONFLICT ON THE TCASII DISPLAY. NO OTHER ACFT COULD BE IDENTED IN THE AREA. ATC WAS ADVISED OF THE RA ACTIONS. NOTE: FOR APPROX 30 SECONDS PRIOR TO THIS EVENT, ATC WAS HAVING AN ONGOING AND CONTINUOUS DIALOGUE WITH A PVT JET THAT WOULD NOT FOLLOW ATC INSTRUCTIONS TO REMAIN AT ALT, SLOW DOWN AND MAKE A 360 DEG TURN.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.