[1] His father Antonios Vlastos was born on 18 October 1858 in Galați, Romania, whose family name origins could be traced to the island of Chios.

The Aéro-Club de France awarded Kostia Vlastos a spherical balloon (sphériques) pilot license (number 287) on 20 November 1913.

[3] When the 1912-13 First Balkan War was declared, the 29-year-old Constantine came to Greece and he volunteered in the Greek Army, thus providing his services for the liberation of the land of his ancestors.

During his service he was accompanied by his brother Stephen A. Vlastos (1885–1960),[4][5] who was a war correspondent for the French newspaper Le Temps using the pseudonym Etienne Labranche.

Kostia Vlastos died in Bourron-Marlotte (Seine-et-Marne) on 28 October 1967 and was buried at the Russian Orthodox cemetery of Sainte-Genevieve-des-Bois outside Paris.