[Q] How to customize a ROM to have airplane mode ON on the first boot after flashing?

Hi all,

I'd like to know how to customize a ROM, so that it can boot for 1st time with airplane mode to be ON?

This is because I don't want any GPRS/EDGE/WIFI data before I know exactly what program can pass a firewall program (manually integrated into the ROM, or installed after boot).

Many thx!

PS: do not use any additional software, because I believe the setting must be INSIDE THE ROM.