Most of the European *A airlines offer this (eg LH, LX and OS). However all of those do not update boarding passes once added to the app.
So during the last few months I have had a couple of these passes added to my iPhone, and for example delays or seat changes are not reflected. Even though I am connected to the internet continuesly.
I very much wonder if A3 has a better implementation. The passbook app offers the functionality to update these boarding passes, it would be very nice if that option is used