Large transport cleared to altitude at which it has conflict with opposite direction traffic.

Attributes
ACN	223619
Time
Date	199210
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : gdl
State Reference	FO
Altitude	msl bound lower : 24000 msl bound upper : 24000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : mmex
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 45 flight time total : 14000 flight time type : 1800
ASRS Report	223619
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 50 flight time total : 6000 flight time type : 50
ASRS Report	223770
Events
Anomaly	conflict : airborne less severe non adherence : published procedure
Independent Detector	other flight crewa
Resolutory Action	none taken : insufficient time
Consequence	Other
Miss Distance	horizontal : 2500 vertical : 100
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

While en route to gdl to mex we were assigned FL230. We climbed to this altitude leveled and then were cleared to FL240 the controller specifically said 'maintain FL240' (as they frequently do in mexico when they want one to change fl). I repeated 'leaving 230 for 240' there was no reply back. We climbed to FL240. Approximately 3-4 mins later an medium large transport passed closely by. I didn't see it but the first officer did. I believe that the controller meant to say to us -- maintain FL230 as the other traffic had apparently been assigned this altitude much earlier and it was appropriate for his direction -- opposite to us.

Original NASA ASRS Text

Title: LGT CLRED TO ALT AT WHICH IT HAS CONFLICT WITH OPPOSITE DIRECTION TFC.

Narrative: WHILE ENRTE TO GDL TO MEX WE WERE ASSIGNED FL230. WE CLBED TO THIS ALT LEVELED AND THEN WERE CLRED TO FL240 THE CTLR SPECIFICALLY SAID 'MAINTAIN FL240' (AS THEY FREQUENTLY DO IN MEXICO WHEN THEY WANT ONE TO CHANGE FL). I REPEATED 'LEAVING 230 FOR 240' THERE WAS NO REPLY BACK. WE CLBED TO FL240. APPROX 3-4 MINS LATER AN MLG PASSED CLOSELY BY. I DIDN'T SEE IT BUT THE FO DID. I BELIEVE THAT THE CTLR MEANT TO SAY TO US -- MAINTAIN FL230 AS THE OTHER TFC HAD APPARENTLY BEEN ASSIGNED THIS ALT MUCH EARLIER AND IT WAS APPROPRIATE FOR HIS DIRECTION -- OPPOSITE TO 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.