Thank you OtherCliff for your reply,
If I try to install the app, Google Play tells me (if translate this the right way from Dutch):
"Librepilot2Go Beta
needs acces to
Location
Media
Bluetooth
Information about device-ID and calls:
With this the app can determine the phone number and device-ID and determine if a call is active and the other number that is being called"
So I guess you are right about that the app should know about an incoming call.
It makes good sense
I will try if the app works in airplane mode. If it does, I guess it will be fine to turn on mobile networking again.
But then again, I wouldn't want to be disturbed by someone calling me when being in the air...
Long story short: I'm installing the app as we speak!