Narrative:

We were on climb out from runway 27R in atl. Cleared to 14000' and in a left turn to 060 degrees. Passing about 9300' we were cleared to 9000'. We reported above 9000' and stopped the climb at about 9600'. An aircraft from our right front passed above and in front of us from right to left. Supplemental information from acn 82772: we broke out of the clouds and saw what we believed to be an large transport at 10000' and approximately 200 yds ahead of us. No evasive action taken. As to why it happened, I believe there was only 1 controller working departure and arrs, and he had too many aircraft to work safely. These 2 aircraft were placed about 10 mi in trail when the first aircraft encountered chop and turbulence. Medium large transport X reduced his airspeed by a factor of mach 10. This speed reduction was unannounced and unauthorized. Large transport Y did not reduce his speed at all when flying through the airspace which medium large transport X had flown through just 2 mins before. The problem was discovered when the difference in airspds was noticed. This speed was at times in excess of 100 KTS. 4 different control instructions were issued to both of these aircraft. Seconds after these instructions the C/a system was activated. Evasive action was not required and loss of ATC sep never occurred. It is not uncommon for aircraft flying through areas of WX to make slight deviations from present heading and airspeed west/O ATC approval. Pilot's must be made aware that even though a deviation might seem slight it could have drastic consequences.

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Original NASA ASRS Text

Title: DEPARTING ACR-LGT CLIMBED TOWARD THE ALT OF ANOTHER ACR-LGT RESULTING IN LESS THAN STANDARD SEPARATION.

Narrative: WE WERE ON CLBOUT FROM RWY 27R IN ATL. CLRED TO 14000' AND IN A LEFT TURN TO 060 DEGS. PASSING ABOUT 9300' WE WERE CLRED TO 9000'. WE RPTED ABOVE 9000' AND STOPPED THE CLB AT ABOUT 9600'. AN ACFT FROM OUR RIGHT FRONT PASSED ABOVE AND IN FRONT OF US FROM RIGHT TO LEFT. SUPPLEMENTAL INFO FROM ACN 82772: WE BROKE OUT OF THE CLOUDS AND SAW WHAT WE BELIEVED TO BE AN LGT AT 10000' AND APPROX 200 YDS AHEAD OF US. NO EVASIVE ACTION TAKEN. AS TO WHY IT HAPPENED, I BELIEVE THERE WAS ONLY 1 CTLR WORKING DEP AND ARRS, AND HE HAD TOO MANY ACFT TO WORK SAFELY. THESE 2 ACFT WERE PLACED ABOUT 10 MI IN TRAIL WHEN THE FIRST ACFT ENCOUNTERED CHOP AND TURB. MLG X REDUCED HIS AIRSPD BY A FACTOR OF MACH 10. THIS SPD REDUCTION WAS UNANNOUNCED AND UNAUTH. LGT Y DID NOT REDUCE HIS SPD AT ALL WHEN FLYING THROUGH THE AIRSPACE WHICH MLG X HAD FLOWN THROUGH JUST 2 MINS BEFORE. THE PROB WAS DISCOVERED WHEN THE DIFFERENCE IN AIRSPDS WAS NOTICED. THIS SPD WAS AT TIMES IN EXCESS OF 100 KTS. 4 DIFFERENT CTL INSTRUCTIONS WERE ISSUED TO BOTH OF THESE ACFT. SECONDS AFTER THESE INSTRUCTIONS THE C/A SYS WAS ACTIVATED. EVASIVE ACTION WAS NOT REQUIRED AND LOSS OF ATC SEP NEVER OCCURRED. IT IS NOT UNCOMMON FOR ACFT FLYING THROUGH AREAS OF WX TO MAKE SLIGHT DEVIATIONS FROM PRESENT HDG AND AIRSPD W/O ATC APPROVAL. PLT'S MUST BE MADE AWARE THAT EVEN THOUGH A DEVIATION MIGHT SEEM SLIGHT IT COULD HAVE DRASTIC CONSEQUENCES.

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.