A B757-200 ON CLBOUT EXPERIENCED A WING PANEL DELAMINATION FELT THROUGH AN AIRFRAME VIBRATION AND VERIFIED VISUALLY. CREW DIVERTED TO NEAREST SUITABLE ARPT.

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UPON CLBING THROUGH 15000 FT; THE ACFT DEVELOPED A VIBRATION. AFTER A SHORT TIME IT ABRUPTLY STOPPED. AROUND THAT TIME WE WERE ADVISED BY OUR FOURTH FLT ATTENDANT THE SHE HEARD AND FELT THE VIBRATION ALSO. WE HAD ONE FLT ATTENDANT CHK TO SEE IF ANYTHING WAS AMISS OUT BY THE ENG NACELLES OR WING AREA. HE RPTED BACK THAT THE WING WAS COMING APART OR SOMETHING TO THAT EFFECT. THIS REALLY GOT OUR ATTENTION SUCH THAT I SENT THE FO BACK TO GET SOME SPECIFICS. HE FOUND THAT THE OUTER LAYER COVERING THE COMPOSITE STRUCTURE OF THE SURFACE BETWEEN THE SPOILERS AND THE TRAILING EDGE FLAPS HAD PEELED BACK AND OFF. FROM HIS VANTAGE POINT; HE COULD NOT TELL THE COMPLETE EXTENT OF THE DAMAGE. HE DID RPT SOME LOOSE BITS FLAPPING IN THE BREEZE. WE SLOWED THE ACFT SO AS TO KEEP FROM LOSING MORE PIECES; AS WELL AS TO KEEP FROM FLYING TOO FAR FROM ZZZ SHOULD WE NEED TO DIVERT (WHICH WAS BECOMING A REALLY GOOD IDEA ABOUT THEN). AFTER TALKING TO MAINT CTL; WE DECIDED TO DIVERT TO ZZZ. WE HELD FOR ABOUT 45 TO 50 MINUTES WITHIN SIGHT OF ZZZ IN ORDER TO BURN DOWN FUEL TO REACH MAX LNDG WT. AN OVERWT LNDG WAS CONSIDERED; BUT AS THE ACFT WAS NOT SHOWING CONTROLLABILITY DIFFICULTIES; WE FELT THAT THE LIGHTER WTS; WITH ASSOCIATED LOWER LNDG SPDS WOULD BE BENEFICIAL. SHOULD THE ACFT PERFORMANCE DEGRADE DURING THE FUEL BURN DOWN; WE WOULD HAVE BEEN ABLE TO MAKE ZZZ IN SHORT ORDER. WE DID HAVE THE FLT ATTENDANT WHO INITIALLY OBSERVED THE DAMAGE TAKE ANOTHER LOOK AND RPT ANY CHANGES. NONE WERE OBSERVED. WE BRIEFED THE FLT ATTENDANTS FOR A PRECAUTIONARY LNDG. WE LANDED AND TAXIED TO THE GATE. UPON REACHING THE GATE; THE MECHANIC HAD ME LOWER THE FLAPS. WE FOUND THAT THE INBOARD 3 FT SECTION OF THE PANEL WAS MISSING. THE FULL EXTENT OF THE DAMAGE COULD NOT BE OBSERVED FROM THE CABIN DURING CRUISE.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE AIRPLANE REQUIRED FULL FLAPS AND R AILERON INPUT TO KEEP THE AIRPLANE LEVEL.