Narrative:

En route from ord to msy at FL280 we almost had a mid air collision with an air carrier Y, B-737. Air carrier X established at cruise when kansas city center issued us an advisory for traffic at our 1 to 2 O'clock position. Shortly thereafter, our TCASII system issued a TA. Upon zooming the TCASII display down to the 5 NM range, the traffic appeared to be at our 12 to 1 O'clock position, within 500 ft of our altitude, closing upon us. TCASII then issued a RA (RA) to 'descend' at least 2000 FPM, followed by an 'increase descent' RA to descend at 3000 FPM. We immediately adhered to both TCASII alerts. The traffic passed in very close proximity directly in front of us. ATC issued an immediate 90 degree turn to the right while all of this occurred. We also adhered to this order. ATC then cleared us back up to FL280 and vectored us back onto our assigned route. Upon landing in msy, the captain called mkc center to find out what happened. Air carrier Y missed us vertically by 700 ft, laterally by 8/10 of 1 NM, according to the ATC center. Air carrier Y was not operating at its assigned altitude.

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Original NASA ASRS Text

Title: ACR X TCASII RA HAD LTSS WITH ACR Y CLB THROUGH OCCUPIED ALT.

Narrative: ENRTE FROM ORD TO MSY AT FL280 WE ALMOST HAD A MID AIR COLLISION WITH AN ACR Y, B-737. ACR X ESTABLISHED AT CRUISE WHEN KANSAS CITY CTR ISSUED US AN ADVISORY FOR TFC AT OUR 1 TO 2 O'CLOCK POS. SHORTLY THEREAFTER, OUR TCASII SYS ISSUED A TA. UPON ZOOMING THE TCASII DISPLAY DOWN TO THE 5 NM RANGE, THE TFC APPEARED TO BE AT OUR 12 TO 1 O'CLOCK POS, WITHIN 500 FT OF OUR ALT, CLOSING UPON US. TCASII THEN ISSUED A RA (RA) TO 'DSND' AT LEAST 2000 FPM, FOLLOWED BY AN 'INCREASE DSCNT' RA TO DSND AT 3000 FPM. WE IMMEDIATELY ADHERED TO BOTH TCASII ALERTS. THE TFC PASSED IN VERY CLOSE PROX DIRECTLY IN FRONT OF US. ATC ISSUED AN IMMEDIATE 90 DEG TURN TO THE R WHILE ALL OF THIS OCCURRED. WE ALSO ADHERED TO THIS ORDER. ATC THEN CLRED US BACK UP TO FL280 AND VECTORED US BACK ONTO OUR ASSIGNED RTE. UPON LNDG IN MSY, THE CAPT CALLED MKC CTR TO FIND OUT WHAT HAPPENED. ACR Y MISSED US VERTICALLY BY 700 FT, LATERALLY BY 8/10 OF 1 NM, ACCORDING TO THE ATC CTR. ACR Y WAS NOT OPERATING AT ITS ASSIGNED ALT.

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.