Narrative:

Controller initially gave us descent to 12000 ft, apparently thinking we were inbound to phoenix. We were at FL290. Before leaving FL290, controller realized we were inbound for tucson instead. He then said 'if you want to stay at FL290 that's fine, discretion to FL270.' captain responded with readback. After handoff to new controller, captain checked in stating FL290 discretion FL270. Controller acknowledged. After departing FL290 for FL270, the controller queried our descent, not realizing the discretionary altitude. No conflicts. I believe the late hour helped attribute to the controller missing the discretionary altitude. Also, upon initial check-in, it took 3 attempts for ATC controller to acknowledge our check-in. I believe he was working multiple sectors and workload may have been another contributing factor. Again, no conflicts with other aircraft.

Google
 

Original NASA ASRS Text

Title: ATC CONFUSED, DISCRETION DSCNT CLRNC, ON MD80 LNDG TUS.

Narrative: CTLR INITIALLY GAVE US DSCNT TO 12000 FT, APPARENTLY THINKING WE WERE INBOUND TO PHOENIX. WE WERE AT FL290. BEFORE LEAVING FL290, CTLR REALIZED WE WERE INBOUND FOR TUCSON INSTEAD. HE THEN SAID 'IF YOU WANT TO STAY AT FL290 THAT'S FINE, DISCRETION TO FL270.' CAPT RESPONDED WITH READBACK. AFTER HDOF TO NEW CTLR, CAPT CHKED IN STATING FL290 DISCRETION FL270. CTLR ACKNOWLEDGED. AFTER DEPARTING FL290 FOR FL270, THE CTLR QUERIED OUR DSCNT, NOT REALIZING THE DISCRETIONARY ALT. NO CONFLICTS. I BELIEVE THE LATE HR HELPED ATTRIBUTE TO THE CTLR MISSING THE DISCRETIONARY ALT. ALSO, UPON INITIAL CHK-IN, IT TOOK 3 ATTEMPTS FOR ATC CTLR TO ACKNOWLEDGE OUR CHK-IN. I BELIEVE HE WAS WORKING MULTIPLE SECTORS AND WORKLOAD MAY HAVE BEEN ANOTHER CONTRIBUTING FACTOR. AGAIN, NO CONFLICTS WITH OTHER ACFT.

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.