Thanks for picking the ball. After reading your post I did the following:
- I cleared cache and cookies of all web browsers, rebooted and logged back in. Was able to save airports as favorites.
- Android: uninstalled the app, rebooted, re-installed and logged back in. After that I was able to synchronize and save airports as favorites.
- Same counts for the iPad: Uninstalled the app, rebooted, reinstalled and logged back in. Now it worked.
Well, a bit cumbersome but successful. Hope this post can help others.
Again, thanks for your pointer.
Cheers