Cellphones are seen everywhere now -- restaurants, supermarkets, cars, sidewalks -- but if you're in an airplane, since the dawn of cellphone time, talking aloft has been forbidden. The reasons behind the ban have been unclear, sometimes citing possible interference with avionics, other times blaming cell-network issues. Now an official panel has been asked by the FAA to study the ban and see if there is any real problem with using the phones and other wireless devices, and if there is, how to fix it. The RTCA, an aviation study group, will investigate the problem and issue its initial report by November. The study group held its first meeting in May and convenes again next month in Washington, D.C. An Advisory Circular issued in October 2000 provides guidance for complying with the current regs regarding portable electronic devices.