Narrative:

Air carrier X was originally climbed to FL330 but stopped at FL290 for air carrier Y traffic. Air carrier X did not read back amended altitude. Traffic was quoted 'at FL310' and air carrier X was told to 'expect higher in 2 mins.' pilot did not question his clearance to FL330 through traffic at FL310.

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Original NASA ASRS Text

Title: ARTCC RADAR CTLR AMENDED AN ACR L1011 ALT TO FL290 DUE TO TFC, A B737 AT FL310. THE L1011 DID NOT READ BACK THE AMENDED ALT AND LTSS OCCURRED.

Narrative: ACR X WAS ORIGINALLY CLBED TO FL330 BUT STOPPED AT FL290 FOR ACR Y TFC. ACR X DID NOT READ BACK AMENDED ALT. TFC WAS QUOTED 'AT FL310' AND ACR X WAS TOLD TO 'EXPECT HIGHER IN 2 MINS.' PLT DID NOT QUESTION HIS CLRNC TO FL330 THROUGH TFC AT FL310.

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.