Narrative:

Air carrier X departed mco climbing to 5000 ft. Air carrier Y was inbound to mco level at 6000 ft. Traffic was issued to air carrier X and he saw the traffic. Air carrier X was told to expect higher shortly. He then started to climb. I noticed air carrier X was out of 5800 asked him if he still had the traffic. He stated yes. By then traffic was no longer a factor. I told him he was only cleared to 5000 ft. He said roger and I climbed him to 12000 ft.

Google
 

Original NASA ASRS Text

Title: ACR X NON ADHERENCE TO ATC CLRNC UNAUTH CLB THROUGH OCCUPIED ALT HAD LTSS FROM ACR Y. PLTDEV.

Narrative: ACR X DEPARTED MCO CLBING TO 5000 FT. ACR Y WAS INBOUND TO MCO LEVEL AT 6000 FT. TFC WAS ISSUED TO ACR X AND HE SAW THE TFC. ACR X WAS TOLD TO EXPECT HIGHER SHORTLY. HE THEN STARTED TO CLB. I NOTICED ACR X WAS OUT OF 5800 ASKED HIM IF HE STILL HAD THE TFC. HE STATED YES. BY THEN TFC WAS NO LONGER A FACTOR. I TOLD HIM HE WAS ONLY CLRED TO 5000 FT. HE SAID ROGER AND I CLBED HIM TO 12000 FT.

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.