This is René Sterne’s main series, consisting of 10 albums, of which you can see sketches, inkings, cover projects, ex-libris and serigraphs in each of their devoted sections in this site. They are all colored by Chantal de Spiegeleer. Here is the official introduction to the series:

Sickened by Hitler’s war madness, Adler deserted from the Luftwaffe in 1942 and found refuge in India. Helped by his friend Helen, he started using his talents as plain pilot to help the oppressed. After the discovery of a treasure, he chooses to settle down in an island in the Pacific Ocean… (Translated from Le Lombard’s website)