Narrative:

In cruise at FL280 20 mi west of czq ZOA instructed us to climb to FL290 and expect FL330 later. After climbing to FL290 and level for approximately 5 mins, ZOA demanded what altitude we were at. After replying FL290 they then instructed us to descend to FL280 and turn right 15 degrees immediately. We saw traffic at 12:00 O'clock position, 4 mi at FL300 crossing left to right. We told ZOA they had instructed us to climb to FL290 and expect FL330 in order to cross the 'complex' in our readback. ZOA replied they had instructed us to maintain FL280. I ask for and received a phone number for oak area B to call on the ground at las vegas. I later called and found out that we had been correct in our readback and the controller was at fault. They thanked us for our quick and prompt action. Before the question of being at the right or wrong altitude we did see the traffic on TCASII and wondered a little why we only had approximately 1000 ft clearance when both aircraft were above FL280. I maybe could have alleviated the situation a little by questioning the controller a min or two earlier. To us as a flight crew there seemed to be enough separation visually but for ATC standards I don't think it was adequate. I will continue to read back all altitude clrncs clearly and question probable conflicts more often.

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Original NASA ASRS Text

Title: AN ACR B737 WAS CLRED TO CLB TO FL290 AND EXPECT FL330 LATER. ARTCC CTLR LATER ASKED THE B737 HIS ALT AND THEN DSNDED HIM TO FL280 AND TURNED HIM 15 DEGS FOR TFC. LTSS OCCURRED SHORTLY THEREAFTER AND THE RPTR ASKED FOR PHONE NUMBER TO CALL THE ZOA UPON LNDG. CALLBACK SHOWED THAT A SYS ERROR HAD OCCURRED AND THE CTLR WAS AT FAULT.

Narrative: IN CRUISE AT FL280 20 MI W OF CZQ ZOA INSTRUCTED US TO CLB TO FL290 AND EXPECT FL330 LATER. AFTER CLBING TO FL290 AND LEVEL FOR APPROX 5 MINS, ZOA DEMANDED WHAT ALT WE WERE AT. AFTER REPLYING FL290 THEY THEN INSTRUCTED US TO DSND TO FL280 AND TURN R 15 DEGS IMMEDIATELY. WE SAW TFC AT 12:00 O'CLOCK POS, 4 MI AT FL300 XING L TO R. WE TOLD ZOA THEY HAD INSTRUCTED US TO CLB TO FL290 AND EXPECT FL330 IN ORDER TO CROSS THE 'COMPLEX' IN OUR READBACK. ZOA REPLIED THEY HAD INSTRUCTED US TO MAINTAIN FL280. I ASK FOR AND RECEIVED A PHONE NUMBER FOR OAK AREA B TO CALL ON THE GND AT LAS VEGAS. I LATER CALLED AND FOUND OUT THAT WE HAD BEEN CORRECT IN OUR READBACK AND THE CTLR WAS AT FAULT. THEY THANKED US FOR OUR QUICK AND PROMPT ACTION. BEFORE THE QUESTION OF BEING AT THE RIGHT OR WRONG ALT WE DID SEE THE TFC ON TCASII AND WONDERED A LITTLE WHY WE ONLY HAD APPROX 1000 FT CLRNC WHEN BOTH ACFT WERE ABOVE FL280. I MAYBE COULD HAVE ALLEVIATED THE SIT A LITTLE BY QUESTIONING THE CTLR A MIN OR TWO EARLIER. TO US AS A FLC THERE SEEMED TO BE ENOUGH SEPARATION VISUALLY BUT FOR ATC STANDARDS I DON'T THINK IT WAS ADEQUATE. I WILL CONTINUE TO READ BACK ALL ALT CLRNCS CLRLY AND QUESTION PROBABLE CONFLICTS MORE OFTEN.

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.