Narrative:

ZAU instructed air carrier X to switch to 132.22 from frequency of 135.7. Radio transmission appeared weak. Captain acknowledged, controller again transmitted the instructions and captain acknowledged and switched to 132.22. Captain checked in on this new frequency. A controller acknowledged air carrier X at FL330. Then air carrier X was instructed to climb to FL350. This was read back by the captain and acknowledged by the first officer who was flying. The first officer set FL350 in altitude MCP. The captain checked the FMC crz page to check altitude capability for weight and temperature. The FMC indicated proper performance and protection. First officer using level change climbed to FL350, after both captain and first officer searched the TCASII returns and visual scans of area ahead of air carrier X. Both wondered about climbing to FL350 but had been instructed, acknowledged, cleared and found no immediate conflict, proceeded as instructed. Was not aware or informed of any conflicting call signs or traffic. After approximately 3-5 mins at FL350, what appeared or sounded like a different controller, asked air carrier X 'when did you check in.' the captain replied that 'air carrier X had checked in, and had been instructed to climb to FL350.' the controller was silent. The captain repeated that air carrier X was at FL350 and wanted ord controller to acknowledge. Captain and first officer continued to scan airspace and TCASII returns for any conflicts. None observed. Controller then said they would get us back down to FL330. Air carrier X was cleared to FL330 and then handed off to another controller at ord. Before handoff controller said that there was possible aircraft identify readback and the clearance could have been for an air carrier Y. However prior to descending us to FL330, controller cleared air carrier Y to FL350 as it appeared we had passed over that flight and he was behind us.

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Original NASA ASRS Text

Title: A BOEING 737 FLC ACCEPTED A CLRNC INTENDED FOR ANOTHER ACFT AND CLBED ABOVE ASSIGNED ALT NEAR DBQ.

Narrative: ZAU INSTRUCTED ACR X TO SWITCH TO 132.22 FROM FREQ OF 135.7. RADIO XMISSION APPEARED WEAK. CAPT ACKNOWLEDGED, CTLR AGAIN XMITTED THE INSTRUCTIONS AND CAPT ACKNOWLEDGED AND SWITCHED TO 132.22. CAPT CHKED IN ON THIS NEW FREQ. A CTLR ACKNOWLEDGED ACR X AT FL330. THEN ACR X WAS INSTRUCTED TO CLB TO FL350. THIS WAS READ BACK BY THE CAPT AND ACKNOWLEDGED BY THE FO WHO WAS FLYING. THE FO SET FL350 IN ALT MCP. THE CAPT CHKED THE FMC CRZ PAGE TO CHK ALT CAPABILITY FOR WT AND TEMP. THE FMC INDICATED PROPER PERFORMANCE AND PROTECTION. FO USING LEVEL CHANGE CLBED TO FL350, AFTER BOTH CAPT AND FO SEARCHED THE TCASII RETURNS AND VISUAL SCANS OF AREA AHEAD OF ACR X. BOTH WONDERED ABOUT CLBING TO FL350 BUT HAD BEEN INSTRUCTED, ACKNOWLEDGED, CLRED AND FOUND NO IMMEDIATE CONFLICT, PROCEEDED AS INSTRUCTED. WAS NOT AWARE OR INFORMED OF ANY CONFLICTING CALL SIGNS OR TFC. AFTER APPROX 3-5 MINS AT FL350, WHAT APPEARED OR SOUNDED LIKE A DIFFERENT CTLR, ASKED ACR X 'WHEN DID YOU CHK IN.' THE CAPT REPLIED THAT 'ACR X HAD CHKED IN, AND HAD BEEN INSTRUCTED TO CLB TO FL350.' THE CTLR WAS SILENT. THE CAPT REPEATED THAT ACR X WAS AT FL350 AND WANTED ORD CTLR TO ACKNOWLEDGE. CAPT AND FO CONTINUED TO SCAN AIRSPACE AND TCASII RETURNS FOR ANY CONFLICTS. NONE OBSERVED. CTLR THEN SAID THEY WOULD GET US BACK DOWN TO FL330. ACR X WAS CLRED TO FL330 AND THEN HANDED OFF TO ANOTHER CTLR AT ORD. BEFORE HDOF CTLR SAID THAT THERE WAS POSSIBLE ACFT IDENT READBACK AND THE CLRNC COULD HAVE BEEN FOR AN ACR Y. HOWEVER PRIOR TO DSNDING US TO FL330, CTLR CLRED ACR Y TO FL350 AS IT APPEARED WE HAD PASSED OVER THAT FLT AND HE WAS BEHIND US.

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.