Narrative:

We were level at FL390 when ATC instructed us to descend to FL350. In the descent, ATC said 'air carrier X, continue descent to FL310 and keep the speed up when you level off.' I answered the clearance and we continued down. Somewhere around FL334 or so, ATC asked us our altitude. I responded with our current altitude and said we were descending down to FL310. ATC told us to turn right to 300 degrees and climb to FL350. He then told the other air carrier aircraft to make a right turn immediately. I told the controller we were climbing to FL350 and that we had been cleared to FL310. There was no response. The next time we heard ATC talk, it was a different controller. The air carrier Y aircraft said he had an a. We also had an RA to climb. I remember seeing a 400 ft difference on the TCAS between us and the other aircraft. I looked out the window and could see the other aircraft at about our 10 O'clock position and about 1-2 mi horizontal distance. I think the problem could have been the fact that there was a third air carrier with similar alpha numeric on the frequency in front of us on his way to phx also. I think the controller might have been wanting our clearance to FL310 to be for the third aircraft. The controller never said we were in the wrong and never gave us a number to contact.

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Original NASA ASRS Text

Title: A SYS ERROR OCCURS WHEN SIMILAR SOUNDING FLT NUMBERS ARE MIXED UP IN A DSCNT CLRNC AND THE RADAR CTLR RELIEVED OF HIS POS AT ZAB, NM.

Narrative: WE WERE LEVEL AT FL390 WHEN ATC INSTRUCTED US TO DSND TO FL350. IN THE DSCNT, ATC SAID 'ACR X, CONTINUE DSCNT TO FL310 AND KEEP THE SPD UP WHEN YOU LEVEL OFF.' I ANSWERED THE CLRNC AND WE CONTINUED DOWN. SOMEWHERE AROUND FL334 OR SO, ATC ASKED US OUR ALT. I RESPONDED WITH OUR CURRENT ALT AND SAID WE WERE DSNDING DOWN TO FL310. ATC TOLD US TO TURN R TO 300 DEGS AND CLB TO FL350. HE THEN TOLD THE OTHER ACR ACFT TO MAKE A R TURN IMMEDIATELY. I TOLD THE CTLR WE WERE CLBING TO FL350 AND THAT WE HAD BEEN CLRED TO FL310. THERE WAS NO RESPONSE. THE NEXT TIME WE HEARD ATC TALK, IT WAS A DIFFERENT CTLR. THE ACR Y ACFT SAID HE HAD AN A. WE ALSO HAD AN RA TO CLB. I REMEMBER SEEING A 400 FT DIFFERENCE ON THE TCAS BTWN US AND THE OTHER ACFT. I LOOKED OUT THE WINDOW AND COULD SEE THE OTHER ACFT AT ABOUT OUR 10 O'CLOCK POS AND ABOUT 1-2 MI HORIZ DISTANCE. I THINK THE PROB COULD HAVE BEEN THE FACT THAT THERE WAS A THIRD ACR WITH SIMILAR ALPHA NUMERIC ON THE FREQ IN FRONT OF US ON HIS WAY TO PHX ALSO. I THINK THE CTLR MIGHT HAVE BEEN WANTING OUR CLRNC TO FL310 TO BE FOR THE THIRD ACFT. THE CTLR NEVER SAID WE WERE IN THE WRONG AND NEVER GAVE US A NUMBER TO CONTACT.

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.