Narrative:

Air carrier X, departed mci for dca, and small transport Y departure mkc eastbound to stl. Both aircraft departure mci airspace approximately the same area. Aircraft were put on parallel headings, and I called ZKC, sector 42, for a higher altitude for air carrier X (I had previously transferred radio communication of small transport Y to ZKC, climbing to 15000 ft). ZKC, sector 42, issued me an altitude of 23000 ft for air carrier X. I issued FL230 to air carrier X, telling him to expedite through 16000 ft for traffic. At this time, both are climbing out of 14000 ft. Air carrier X to 23000 ft, and small transport Y to what I believed 15000 ft. Unknown to me, ZKC had climbed small transport Y to 23000 ft, his requested altitude. When air carrier X was climbing out of 16000 ft, I observed small transport Y at 15000 ft. I then turned air carrier X to a heading (converging) to join the SID, believing I had 1000 ft altitude separation, and growing. Leaving 16000 ft, air carrier X slowed the rate of climb and small transport Y climbed at a better than normal rate inside ZKC airspace. Air carrier X and small transport Y converged to 3.5 NM and 600 ft separation. Human factors: during coordination with ZKC, I had told the controller that air carrier X was eastbound to 'get around' small transport Y. ZKC took that to mean I was going to leave him on a eastbound heading, not turn him to join the SID, which we must do according to our LOA, so he continued small transport Y climb to 23000 ft.

Related reports:

Google
 

Original NASA ASRS Text

Title: SMT Y CLB TO OCCUPIED ALT HAD LTSS FROM ACR X. SYS ERROR.

Narrative: ACR X, DEPARTED MCI FOR DCA, AND SMT Y DEP MKC EBOUND TO STL. BOTH ACFT DEP MCI AIRSPACE APPROX THE SAME AREA. ACFT WERE PUT ON PARALLEL HDGS, AND I CALLED ZKC, SECTOR 42, FOR A HIGHER ALT FOR ACR X (I HAD PREVIOUSLY TRANSFERRED RADIO COM OF SMT Y TO ZKC, CLBING TO 15000 FT). ZKC, SECTOR 42, ISSUED ME AN ALT OF 23000 FT FOR ACR X. I ISSUED FL230 TO ACR X, TELLING HIM TO EXPEDITE THROUGH 16000 FT FOR TFC. AT THIS TIME, BOTH ARE CLBING OUT OF 14000 FT. ACR X TO 23000 FT, AND SMT Y TO WHAT I BELIEVED 15000 FT. UNKNOWN TO ME, ZKC HAD CLBED SMT Y TO 23000 FT, HIS REQUESTED ALT. WHEN ACR X WAS CLBING OUT OF 16000 FT, I OBSERVED SMT Y AT 15000 FT. I THEN TURNED ACR X TO A HDG (CONVERGING) TO JOIN THE SID, BELIEVING I HAD 1000 FT ALT SEPARATION, AND GROWING. LEAVING 16000 FT, ACR X SLOWED THE RATE OF CLB AND SMT Y CLBED AT A BETTER THAN NORMAL RATE INSIDE ZKC AIRSPACE. ACR X AND SMT Y CONVERGED TO 3.5 NM AND 600 FT SEPARATION. HUMAN FACTORS: DURING COORD WITH ZKC, I HAD TOLD THE CTLR THAT ACR X WAS EBOUND TO 'GET AROUND' SMT Y. ZKC TOOK THAT TO MEAN I WAS GOING TO LEAVE HIM ON A EBOUND HDG, NOT TURN HIM TO JOIN THE SID, WHICH WE MUST DO ACCORDING TO OUR LOA, SO HE CONTINUED SMT Y CLB TO 23000 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.