Narrative:

Aircraft X was climbing out of the low sector and aircraft Y was level at FL260 wbound. Temporary altitude FL250 was input in aircraft X's data block. When aircraft X checked in he said he was out of FL240 for FL260. I did not hear the FL260. Every indication was that he was climbing to FL250. The data block said it, the strip said it, and the controller I relieved said it. I thought he was climbing to FL250. The controller in the low sector had mistakenly climbed aircraft X to FL260. Supplemental information from acn 391005: aircraft X reported on agc sector, climbed to FL230 by previous controller. The sector was previously combined with bsv sector. I flashed aircraft X data block at air sector. Air sector controller computer input temporary altitude FL250. I climbed aircraft X to FL260 and then switched him to air. I could have sworn that I climbed aircraft X to FL250. I would have bet my life on it. I listened to the tape, and very clearly I could hear myself climbing aircraft X to FL260. Supplemental information from acn 391135: I checked in with ZOB, requested FL260 (filed FL310), cleared to FL230. Second ZOB controller cleared me to FL260. Checked in with third ZOB controller advised 'FL240 climbing to FL260,' he acknowledged. He later asked 'verify level at FL250.' I replied 'negative, climbing to FL260' (out of approximately FL256). He told me I had only been cleared to FL250 'descend immediately.' I descended abruptly and informed him I had been cleared to FL260, and checked in climbing to FL260. Spoke to a supervisor at ZOB after landing. He told me he had reviewed the tapes, and I was cleared to FL260 and I did check in climbing to FL260.

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Original NASA ASRS Text

Title: A HEARBACK READBACK SYS ERROR OCCURRED BTWN TWO ARTCC CTLRS. THE INITIAL ERROR OCCURRED WITH THE LOW ALT CTLR WHEN A C500 PLT REQUESTED CLB TO FL260. THE LOW ALT CTLR INPUT FL250 INTO THE COMPUTER, WROTE FL250 ON THE CTL DATA STRIP, BUT CLRED THE ACFT TO FL260.

Narrative: ACFT X WAS CLBING OUT OF THE LOW SECTOR AND ACFT Y WAS LEVEL AT FL260 WBOUND. TEMPORARY ALT FL250 WAS INPUT IN ACFT X'S DATA BLOCK. WHEN ACFT X CHKED IN HE SAID HE WAS OUT OF FL240 FOR FL260. I DID NOT HEAR THE FL260. EVERY INDICATION WAS THAT HE WAS CLBING TO FL250. THE DATA BLOCK SAID IT, THE STRIP SAID IT, AND THE CTLR I RELIEVED SAID IT. I THOUGHT HE WAS CLBING TO FL250. THE CTLR IN THE LOW SECTOR HAD MISTAKENLY CLBED ACFT X TO FL260. SUPPLEMENTAL INFO FROM ACN 391005: ACFT X RPTED ON AGC SECTOR, CLBED TO FL230 BY PREVIOUS CTLR. THE SECTOR WAS PREVIOUSLY COMBINED WITH BSV SECTOR. I FLASHED ACFT X DATA BLOCK AT AIR SECTOR. AIR SECTOR CTLR COMPUTER INPUT TEMPORARY ALT FL250. I CLBED ACFT X TO FL260 AND THEN SWITCHED HIM TO AIR. I COULD HAVE SWORN THAT I CLBED ACFT X TO FL250. I WOULD HAVE BET MY LIFE ON IT. I LISTENED TO THE TAPE, AND VERY CLEARLY I COULD HEAR MYSELF CLBING ACFT X TO FL260. SUPPLEMENTAL INFO FROM ACN 391135: I CHKED IN WITH ZOB, REQUESTED FL260 (FILED FL310), CLRED TO FL230. SECOND ZOB CTLR CLRED ME TO FL260. CHKED IN WITH THIRD ZOB CTLR ADVISED 'FL240 CLBING TO FL260,' HE ACKNOWLEDGED. HE LATER ASKED 'VERIFY LEVEL AT FL250.' I REPLIED 'NEGATIVE, CLBING TO FL260' (OUT OF APPROX FL256). HE TOLD ME I HAD ONLY BEEN CLRED TO FL250 'DSND IMMEDIATELY.' I DSNDED ABRUPTLY AND INFORMED HIM I HAD BEEN CLRED TO FL260, AND CHKED IN CLBING TO FL260. SPOKE TO A SUPVR AT ZOB AFTER LNDG. HE TOLD ME HE HAD REVIEWED THE TAPES, AND I WAS CLRED TO FL260 AND I DID CHK IN CLBING TO FL260.

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.