A keen sportsman, he was an energetic secretary general of the oldest gymnastic society in Paris, that of the XVIieme arrondissement.

(The first licenses were given to prominent aviators without any formal test) He later became one of the chief instructors, and also made proving flights of newly produced Blériot aircraft.

[3] In August 1910, flying a Gnome-engined Blériot XI, he won the Circuit de l'Est, covering the 805 km (500 mi) in 12hr 1 min 1 sec, an average speed of 66.99 km/h (41.63 mph)[4] Leblanc was first in the race and Émile Aubrun finished second.

[6] In November 1910, he represented France in the Gordon Bennett Trophy race for airplanes, held in New York, but misjudged a turn on his last lap, and crashed: had he not done so, he would have won the competition, which was won by Claude Grahame-White, also flying a Blériot.

[citation needed] In 1919, he was appointed manager of the Compagnie des Messageries Aeriennes, an airline formed by the major French aircraft manufacturers in order to create a civil aviation market, and he was also put in charge of the Societe des Stocks, which was formed to dispose of the large number of surplus aircraft and aero-engines resulting from the end of the First World War.