Narrative:

I had just started working sector 5R and D combined. The amount of traffic increased dramatically after I sat down. Aircraft were deviating around WX buildups around anchorage. There were 2 aircraft crossing the sector (1 landing) in an unusual manner. 1 aircraft called for VFR advisories before the error. The error: the 2 aircraft departed anc; both swbound; both requesting FL280. After issuing the altitude clearance to both aircraft (they were separated by greater than 10 mi at the time); I noticed the overtake. I asked the rear aircraft if he could climb to FL300. He responded no because he was non rvsm (he had filed contrary to this). I changed his type/suffix in the computer then issued a clearance to the front aircraft to maintain FL260 (thinking the rear aircraft would climb above the front one). I was distraction by several other aircraft calling (including the VFR pop-up) and did not notice until too late that an error had occurred. I asked the rear aircraft to turn; then put him back on course when I had vertical separation. No collision alert ever sounded. I turned the error in to my supervisor at this time.

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Original NASA ASRS Text

Title: ZAN CTLR EXPERIENCED OPERROR WITH 2 SUCCESSIVE DEPS CLBING TO FL260 THE SECOND ACFT FASTER THAN THE FIRST.

Narrative: I HAD JUST STARTED WORKING SECTOR 5R AND D COMBINED. THE AMOUNT OF TFC INCREASED DRAMATICALLY AFTER I SAT DOWN. ACFT WERE DEVIATING AROUND WX BUILDUPS AROUND ANCHORAGE. THERE WERE 2 ACFT XING THE SECTOR (1 LNDG) IN AN UNUSUAL MANNER. 1 ACFT CALLED FOR VFR ADVISORIES BEFORE THE ERROR. THE ERROR: THE 2 ACFT DEPARTED ANC; BOTH SWBOUND; BOTH REQUESTING FL280. AFTER ISSUING THE ALT CLRNC TO BOTH ACFT (THEY WERE SEPARATED BY GREATER THAN 10 MI AT THE TIME); I NOTICED THE OVERTAKE. I ASKED THE REAR ACFT IF HE COULD CLB TO FL300. HE RESPONDED NO BECAUSE HE WAS NON RVSM (HE HAD FILED CONTRARY TO THIS). I CHANGED HIS TYPE/SUFFIX IN THE COMPUTER THEN ISSUED A CLRNC TO THE FRONT ACFT TO MAINTAIN FL260 (THINKING THE REAR ACFT WOULD CLB ABOVE THE FRONT ONE). I WAS DISTR BY SEVERAL OTHER ACFT CALLING (INCLUDING THE VFR POP-UP) AND DID NOT NOTICE UNTIL TOO LATE THAT AN ERROR HAD OCCURRED. I ASKED THE REAR ACFT TO TURN; THEN PUT HIM BACK ON COURSE WHEN I HAD VERT SEPARATION. NO COLLISION ALERT EVER SOUNDED. I TURNED THE ERROR IN TO MY SUPVR AT THIS TIME.

Data retrieved from NASA's ASRS site as of January 2009 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.