I was checking out if I needed to do "airplane mode" on my cell, what do you tink?

and also it said that it would automatically go to airplane because of the pits interference and I did not have to do it , so this raised another question.. on 911 when the people supposedly called their families, how did they do that.. according to what I read, personal cell phones do not work on airplanes.. I am now very curious... any REAL help here?