I heard new report on cell-phone used on air-plane. those of phone signals may cause more troubleduring operation plane. there wireless instrument operated battery including Ipod, Cell phone, and Note book and P.M.P might disturb Air-plane navigation and Global positioning system. especially it is fatal to use cell phone during taking off and landing.  there are varieties of examples  to disturb transmitting between pilot and control tower. passenger with wireless instruments definitely should not be on the cell-phone  during taking off and landing. it will be a tragic death. I recently took a plane from Inchon to Busan. Flight attendante requested all passengers not to use wireless instrument operated battery during taking off and lading well, I am so afraid that my cell phone  turned off and Mp player also  stopped and turn off. I am not what will happen by my cellphone.