User blog comment:EmpyreanSmoke/How did Cas survive the fall?/@comment-95.115.164.131-20150711012651

All the angels except Micheal and Lucifer (since the spell had no effect on them- unlike all the other angels, there were not expelled to the earth) were expelled to the earth. But Cas was already human when the spell was casted and Metatron just apported him to the earth. So basically, he was already just a human watching the angels fall.