Narrative:

Flight operating oma-stl. While inbound on the rivers 1 arrival between irk and uin and at assigned altitude FL240, the following event transpired. TCASII showed a red TA at approximately 11-12 O'clock, 1600 ft above, but descending. Sighting visually, I observed 2 military fgt types, in loose formation, crossing the flight path from left to right at approximately 90 degree angle and higher. Immediately thereafter the TCASII aural alert sounded 'descend, descend.' the captain commanded descend, I disengaged the autoplt and pushed the aircraft over to descend. I looked up and saw a third military aircraft at 11:30 position, in a hard left bank and climb. This aircraft was slightly above and in front, passing left to right. After this aircraft cleared and with no further TCASII alerts I pulled back up to altitude. An inquiry was made of ZKC about the flight and the controller advised of a military flight at FL250. I believe without the TCASII a midair might have occurred. It appeared that at least one of the military aircraft in the flight was not at his assigned altitude.

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Original NASA ASRS Text

Title: MLG IN PCA HAS TCASII RA, RESPONDS.

Narrative: FLT OPERATING OMA-STL. WHILE INBOUND ON THE RIVERS 1 ARR BTWN IRK AND UIN AND AT ASSIGNED ALT FL240, THE FOLLOWING EVENT TRANSPIRED. TCASII SHOWED A RED TA AT APPROX 11-12 O'CLOCK, 1600 FT ABOVE, BUT DSNDING. SIGHTING VISUALLY, I OBSERVED 2 MIL FGT TYPES, IN LOOSE FORMATION, XING THE FLT PATH FROM L TO R AT APPROX 90 DEG ANGLE AND HIGHER. IMMEDIATELY THEREAFTER THE TCASII AURAL ALERT SOUNDED 'DSND, DSND.' THE CAPT COMMANDED DSND, I DISENGAGED THE AUTOPLT AND PUSHED THE ACFT OVER TO DSND. I LOOKED UP AND SAW A THIRD MIL ACFT AT 11:30 POS, IN A HARD L BANK AND CLB. THIS ACFT WAS SLIGHTLY ABOVE AND IN FRONT, PASSING L TO R. AFTER THIS ACFT CLRED AND WITH NO FURTHER TCASII ALERTS I PULLED BACK UP TO ALT. AN INQUIRY WAS MADE OF ZKC ABOUT THE FLT AND THE CTLR ADVISED OF A MIL FLT AT FL250. I BELIEVE WITHOUT THE TCASII A MIDAIR MIGHT HAVE OCCURRED. IT APPEARED THAT AT LEAST ONE OF THE MIL ACFT IN THE FLT WAS NOT AT HIS 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.