The chief pilot for the French Wright Company, Lefebvre was a participant in the first international air race, the Grande Semaine d'Aviation at Reims in 1909, piloting a Wright Flyer. He, Louis Blériot and Hubert Latham were selected as France's representatives during the contest for the Gordon Bennett Trophy on 22 August, after poor weather made the morning's planned qualifying run impossible. When the weather lifted around 6 o'clock that evening, Lefebvre was one of the pilots who took to the sky in an exhibition, giving one of the earliest displays of stunt flying. The New York Times described his maneuvers thus: "Lefebvre...came driving at the crowded tribunes, turned in the nick of time, went sailing off, swooped down again till he made the flags on the pillars and the plumes on the ladies' hats flutter, and so played about at will for our applause." He was subsequently fined $4 by the judges for displaying excessive "recklessness and daring." During the running of the race, he placed fourth, behind Glenn Curtiss, Blériot and Latham.
Only nine days after the end of the Reims event, Lefebvre was killed in a crash at Juvisy, when the plane he was testing dropped to the ground from a height of twenty feet. In so doing, he became the first person to die while piloting a powered airplane, and the second person to be killed in an airplane crash.