Narrative:

I was PNF. Both pilots were listening to center frequency. Shortly after reaching FL230, ZLA asked to 'descend and maintain 17000', altimeter 29.96, best rate of descent, please.' both pilots heard this clearance and I read back the clearance to ZLA. At approximately 19500' MSL, center asked us what altitude we were at. We responded. Center replied 'sorry about that,' then asked us to climb and maintain FL230. Upon reaching this altitude, I asked center if we had in fact been cleared to 17000', or if there was someone else on the frequency with the same call sign. He said that we were never given a clearance to 17000' MSL, and that another air carrier had been given that clearance. He then replied again 'sorry about that.' mins later, during our frequency handoff, ZLA for the third time apologized. Upon reaching our destination (las), my captain was curious and called ZLA. Center said that they never heard our readback and that the tapes did not need to be played back because there was no traffic conflict. Supplemental information from acn 127789: on a controller's screen, X airlines (xx), Y airlines (formerly xy, now ab), and Z airlines (zx) are apparently similar enough that controllers often give one company's name and another's flight #. Also, when a controller is working 2 frequencys, it is impossible to know what the controllers is saying or listening to on the other frequency. Calls and readbacks are often missed. Full call sign and full clearance readbacks are definitely required.

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Original NASA ASRS Text

Title: ACR RECEIVES, READS BACK CLRNC TO DESCEND FROM FL230. AFTER 4500' DESCENT, CTLR ASKED ALT AND THEN 'SORRY ABOUT THAT.' REQUESTS CLIMB AND MAINTAIN FL230. APOLOGIZES 2 MORE TIMES DURING SUBSEQUENT COM.

Narrative: I WAS PNF. BOTH PLTS WERE LISTENING TO CENTER FREQ. SHORTLY AFTER REACHING FL230, ZLA ASKED TO 'DSND AND MAINTAIN 17000', ALTIMETER 29.96, BEST RATE OF DSCNT, PLEASE.' BOTH PLTS HEARD THIS CLRNC AND I READ BACK THE CLRNC TO ZLA. AT APPROX 19500' MSL, CENTER ASKED US WHAT ALT WE WERE AT. WE RESPONDED. CENTER REPLIED 'SORRY ABOUT THAT,' THEN ASKED US TO CLB AND MAINTAIN FL230. UPON REACHING THIS ALT, I ASKED CENTER IF WE HAD IN FACT BEEN CLRED TO 17000', OR IF THERE WAS SOMEONE ELSE ON THE FREQ WITH THE SAME CALL SIGN. HE SAID THAT WE WERE NEVER GIVEN A CLRNC TO 17000' MSL, AND THAT ANOTHER ACR HAD BEEN GIVEN THAT CLRNC. HE THEN REPLIED AGAIN 'SORRY ABOUT THAT.' MINS LATER, DURING OUR FREQ HDOF, ZLA FOR THE THIRD TIME APOLOGIZED. UPON REACHING OUR DEST (LAS), MY CAPT WAS CURIOUS AND CALLED ZLA. CENTER SAID THAT THEY NEVER HEARD OUR READBACK AND THAT THE TAPES DID NOT NEED TO BE PLAYED BACK BECAUSE THERE WAS NO TFC CONFLICT. SUPPLEMENTAL INFO FROM ACN 127789: ON A CTLR'S SCREEN, X AIRLINES (XX), Y AIRLINES (FORMERLY XY, NOW AB), AND Z AIRLINES (ZX) ARE APPARENTLY SIMILAR ENOUGH THAT CTLRS OFTEN GIVE ONE COMPANY'S NAME AND ANOTHER'S FLT #. ALSO, WHEN A CTLR IS WORKING 2 FREQS, IT IS IMPOSSIBLE TO KNOW WHAT THE CTLRS IS SAYING OR LISTENING TO ON THE OTHER FREQ. CALLS AND READBACKS ARE OFTEN MISSED. FULL CALL SIGN AND FULL CLRNC READBACKS ARE DEFINITELY REQUIRED.

Data retrieved from NASA's ASRS site as of August 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.