i saw some threads about plane-mode in this forum before, so here what i know..
psiloc systemtools has a planemode to use the phone in an airplane..and it finay works after the last sendo update... the problem is, that the mp3 player does not work with systemtools. you have to update the realplayer with the HelixPlayer-Symbian-Series60-v1.0 so you can listen to mp3 with the helixplayer. i think its the only app for audio working in planemode...
have a nice flight :)
bst

was told by easyjet today that no phones can be used in flight mode, to be switched off completety just got back from scotland

in plane-mode its not a phone anymore... ; )
it s not looking for network or doing other "dangerous" things.
so you can not use any electronic device. not even a mp3-player.