How to boot Android with flight mode (airplane mode) activated Is it possible to boot up Android so flight mode is activated?

When I set airplane mode before rebooting or creating a nandroid backup the setting will stick.

Are there any files like init.d that are easy to modify where these kinds of boot options are stored?
Another alternative would be a modified Custom Recovery. But I haven't heard of one.

Use case:
Restore an old Nandroid Backup, but before the system fetches all the updates (messenger...) the user wants to restore certain app data so nothing gets lost.  

That is only possible when in flight mode.
An indirect possibility would be using tasker, which has the capability of performing actions "on device start" (amongst many others). So you could setup a profile that says: "on device start" → "set airplane mode on". Other automation apps like llama might have the same capability.

Note however that the action can of course only be executed as soon as the app (Tasker/ Llama) is started, so there might be a delay in which airplane mode is turned off (and a network connection available). If you need to safely rule that out: take out the SIM card, and delete the AP config for your WiFi. That way the device would still boot with airplane mode disabled – but had no chance to connect anywhere. Third option would be booting it while inside a Faraday cage (or a lead box) …