German book blogger Stephi wrote a beautiful review, in German.
This is an English translation:
This book is absolutely beautiful and impresses with its simplicity. Even small children can engage with the topic of flight and think about how you can make other people happy with a small friendly gesture. My children love it just as much as I do and I think that’s simply because of the great overall pact, the simple stories that touch the heart, the great pictures and the fact that my kids just love numbers and counting. I can really warmly recommend this beautifully illustrated picture book to you!