Križaj was born in Kopriva on the Karst Plateau, then part of the Austro-Hungarian county of Gorizia and Gradisca.

Already at a young age he showed a passion for flight, which led him to pursue a pilot's course at the royal officer school in Capua near Naples, Italy.

Due to his Slovene ethnic origins, he was not allowed into the regular Italian Royal Air Force, but he was nevertheless granted a place in the reserves.

Because of the physical hardships endured during the training and his pro-Slovenian and pro-Yugoslav national political stance, he flew a Fiat AS.1 airplane on 25 June 1932 from Udine to Ljubljana, crossing the border of Yugoslavia, which led to much media interest.

His life ended on 8 October 1948, when his aircraft, a Yakovlev Yak-3, crashed into Mount Snežnik in southwestern Slovenia because of poor visibility in dense fog.