CTLR RPT AND FLC RPT REGARDING ACFT WHICH CLBED TO FL350 THEN COULD NOT MAINTAIN SPD. THEY REQUESTED LOWER AND TOLD UNABLE DUE TO TFC BELOW. THEY DSNDED. DSCNT WITHOUT CLRNC. ALTDEV.

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ACR MLG TOOK FOREVER TO CLB TO FL350. HE WAS THERE (AT FL350) FOR ABOUT 1 MIN WHEN HE CALLED ON FREQ AND SAID HE HAD TO DSND. I TOLD THE FLT 'UNABLE' AND POINTED OUT SEVERAL PIECES OF TFC THAT WERE IN CONFLICT WITH HIM AT FL330. ABOUT 30 SECONDS LATER MLG XMITS THAT HE WILL BE DSNDING IMMEDIATELY. I OBSERVE THAT HE IS BARELY CLR OF ACR OFF TO HIS L SIDE. I TELL HIM 'OK' AND ASK IF THERE IS A PROB. THE REPLY WAS; 'TOO HOT; TOO HVY; WE CAN'T KEEP OUR SPD.' PERHAPS THE FLC SHOULD HAVE DOUBLE CHKED THEIR 'VITALS' (WT; FUEL; TEMP) BEFORE ASKING FOR AN ALT THAT THE PLANE CAN'T FLY. A 10 SECOND VARIATION IN TIMES FOR EITHER ACFT COULD HAVE RESULTED IN A POSSIBLE CATASTROPHE. THIS DSCNT DID RESULT IN A SIT OF LTSS. SUPPLEMENTAL INFO FROM ACN 341230: UPON REACHING 35000 FT; AIRSPD BEGAN TO DETERIORATE; CAPT REQUESTED DSCNT CLRNC. ZDC ASKED IF 'THERE WAS SOMETHING WE SHOULD KNOW ABOUT.' CAPT RESPONDED THAT 'THE TEMP WAS WARMER THAN STANDARD' AND WE WERE REQUESTING LOWER. WE WERE CLRED TO FL260 BY CTR. PROB -- TEMP WARMER THAN STANDARD AS RPTED.