Jailler was promoted to
Caporal on 23 March 1915. Shortly thereafter, he was finally assigned a flying slot on 1 April 1915, when he was assigned to Escadrille 15. He then was promoted to
Sergent ten days after joining his new unit. On 16 May 1915, he was seriously wounded in combat. Five days later, he was awarded the
Médaille militaire. It was 8 March 1916 before he scored his first win. He then added erratically to his score until 12 June 1917, when he scored his twelfth. During July 1916, after Jailler shot down a German
observation balloon for his fourth win, he was promoted to
Adjutant. On 8 July, he was also appointed a ''
Chevalier de la Légion d'honneur''. He would score twice more that year, to end the year an ace. Jailler was commissioned a
sous lieutenant on 22 August 1917. On 23 November 1917, he was pulled from combat for a rest, after 232 flying hours and 27 dogfights, and became an instructor. ==Post World War I==