HOW can i enable my "ipad" airplane mode BEFORE i unlock it?
You can’t for a couple reasons.


Networking works while the device is locked
You can’t operate the device until it’s unlocked


Your best bet is to power off the device immediately and take it to where there is no WiFi to which you are pre-connected (power off that WiFi that are set up or move away from them all). Also, consider if you have cellular service, disable that or remove the SIM or go away from coverage (in a faraday cage if you can) before you unlock the device to make changes.