Accelerator was collapsed atop a hill.

Neither Last Order nor Misaka Worst was there. Only the white snow stretched on seemingly forever around him. At an altitude of 8000 meters, he had been struck by the mass of strange energy fired by the fortress, but not even he really understood what had happened after that. The white wings had disappeared from his back. At the very least, he understood that he was alive like that because the great destruction had been stopped at the last second.

A Certain Magical Index Volume 22, pg. 161