@ovcijisir
Here is my experience when trying to create wallets on airplane mode on Blocksktream Green and Blue Wallet.

Blockstream Green:
The app asked for my biometrics (fingerprint) at the beginning of the setup process. I had two options: to provide it by touching my fingerprint sensor or click the "Cancel" button. I clicked cancel and entered a 6-digit PIN code instead. The software started creating the wallet but it failed and I saw the "Network error" message you mentioned. I tried two more times and got the same error.

Then I went back to the beginning and provided my biometric data. Blockstream Green generated the wallet immediately. So, if the software gives you the option to provide your biometrics to unlock it, you should provide it. That's what worked for me.

Blue Wallet:
I had no issues logging in to my existing Blue Wallet app and generate a new wallet and seed in airplane mode. It shows a syncing notification that doesn't go away but that's normal since the app doesn't have internet connection and can't connect to a server.