Air carrier Y was issued a descent through an occupied altitude.

Attributes
ACN	109054
Time
Date	198904
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : vhp
State Reference	IN
Altitude	msl bound lower : 28000 msl bound upper : 30000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zid
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 8
ASRS Report	109054
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	none taken : insufficient time
Consequence	faa : investigated
Miss Distance	horizontal : 27600 vertical : 1100
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Traffic at ind high sector was moderate. The majority of the traffic was inbound to chicago area airports. WX was no factor. Air carrier X departed cvg-tth-slc, and called on at XX36Z. He was climbed to FL290 and later turned west heading 280 degrees. Air carrier Y called at XX15Z at FL310 well west of course and proceeding direct but-ord. The ord traffic was bunched up south of vhp and the area supervisor and I were discussing which 2 aircraft would be re-routed over rbs-ord to relieve the traffic jam. The C/a activated between air carrier Y and air carrier Z, both at FL310. Air carrier X's data block was covered by other data blocks. I descended air carrier Y to FL280 to avoid air carrier Z on J80 wbound. C/a between air carrier Y and air carrier X activated only after both targets were diverging and air carrier Y had violated air carrier X's airspace.

Original NASA ASRS Text

Title: ACR Y WAS ISSUED A DESCENT THROUGH AN OCCUPIED ALT.

Narrative: TFC AT IND HIGH SECTOR WAS MODERATE. THE MAJORITY OF THE TFC WAS INBND TO CHICAGO AREA ARPTS. WX WAS NO FACTOR. ACR X DEPARTED CVG-TTH-SLC, AND CALLED ON AT XX36Z. HE WAS CLBED TO FL290 AND LATER TURNED W HDG 280 DEGS. ACR Y CALLED AT XX15Z AT FL310 WELL W OF COURSE AND PROCEEDING DIRECT BUT-ORD. THE ORD TFC WAS BUNCHED UP S OF VHP AND THE AREA SUPVR AND I WERE DISCUSSING WHICH 2 ACFT WOULD BE RE-ROUTED OVER RBS-ORD TO RELIEVE THE TFC JAM. THE C/A ACTIVATED BTWN ACR Y AND ACR Z, BOTH AT FL310. ACR X'S DATA BLOCK WAS COVERED BY OTHER DATA BLOCKS. I DSNDED ACR Y TO FL280 TO AVOID ACR Z ON J80 WBOUND. C/A BTWN ACR Y AND ACR X ACTIVATED ONLY AFTER BOTH TARGETS WERE DIVERGING AND ACR Y HAD VIOLATED ACR X'S AIRSPACE.

Data retrieved from NASA's ASRS site as of August 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.