Raoul Lufbery was the best-known American pilot in World War I, but he’s been relegated to obscurity by a mysterious past.

On a warm May afternoon in France in 1918, miles from the combat zone, you could almost forget the world was at war. From the ground, the sight of two biplanes turning and twisting in the sky might have seemed part of a fantastic show — until a tiny figure fell from his plane and plummeted to Earth.

None of the witnesses to the horrifying scene could believe the man was Gervais Raoul Lufbery, America’s ace fighter pilot. He had defied the odds and outlived most of his comrades, but at his funeral, fellow pilots reflected on the fact that they hadn’t known the dogged fighter at all.

His dream was to avoid a mediocre existence.

“In contrast to him, the Sphinx was a child’s primer,” pilot Edwin Parsons mused. “He kept his real self shut up like a clam in a shell.”

Lufbery’s death grabbed international headlines, but history has remained silent on his considerable contributions. The truth is, he just didn’t fit the mold of a World War I hero.

Born in 1885, Lufbery grew up in a tiny French village with his grandparents. His mother, who was French, died when he was a baby, and his American father dropped out of sight for most of his upbringing. Armed with a sixth-grade education and fascination with Jules Verne, Lufbery had few prospects.

But even as a teenager, he wanted more. As one friend later wrote, “His dream was to avoid a mediocre existence.”

At 20, Lufbery started to travel the world, grabbing odd jobs — from nurse to racecar driver to dockworker — along the way.

Unlike many Europeans of his time, Lufbery made an effort to get to know his new homes from a native’s point of view. He picked up languages with uncanny speed as he traveled through North Africa, the Mediterranean, the Balkans, Cuba, South Asia and the United States — where he became an American citizen.

He swore to avenge his friend’s death by becoming a pilot.

In 1910, while working in India, Lufbery met the person who would change his life forever — Marc Pourpe, a French aviator who was putting on airshows in Calcutta. Like most people at the time, Lufbery had never seen an airplane. Undaunted, he approached the aviator and requested a job as his mechanic.

Pourpe asked Lufbery if he knew anything about airplane engines. Lufbery shrugged before responding, “Were you competent the first day you worked on an engine? No.”

Impressed by his brash attitude, Pourpe hired Lufbery, ensuring he studied aircraft mechanics, and the pair spent years flying around Southeast Asia and Africa, where Pourpe made the first round-trip flight between Egypt and Sudan.

They returned to France in August 1914 expecting a hero’s welcome, but they’d been bumped from the headlines by the outbreak of World War I. Pourpe joined up immediately, pulling strings to get Lufbery in as his mechanic in the French Air Force. Just four months later, Pourpe was killed in a plane crash.

The circumstances surrounding the crash were unclear, but Lufbery swore to avenge his friend’s death by becoming a pilot.

Ironically, the man who would become one of the greatest war pilots had a dismal start. Lufbery’s instructors bemoaned his heavy-handedness and begged him to stop flying. But he ignored them and honed his skills, so much so that he was recruited in 1916 by the Lafayette Escadrille, an elite group of American Ivy Leaguers volunteering in the French Air Force, which needed men with flying expertise.

The Escadrille’s experience of the war was about as far from the trenches as you could get. Funded by American magnates like J.P. Morgan, the squadron lived luxuriously, drinking cocktails and sleeping in chateaus. They even had mascots — lion cubs Whiskey and Soda, with whom the reclusive Lufbery would play for hours. But the Americans saw their share of action — and once airborne, Lufbery proved he had an unparalleled talent for killing and quickly set himself apart as the squadron’s leading ace.

Lufbery understood it wasn’t about guts and glory, and that even the best pilots couldn’t be protected by shiny medals or fawning headlines.

When the U.S. entered the war in 1917, many Escadrille pilots, Lufbery included, finally got their chance to fly for Uncle Sam.

Eddie Rickenbacker, who regarded Lufbery as a mentor and would eventually take his place as the leading American ace, marveled at Lufbery’s prowess. For his part, Lufbery showed no interest in counting his kills, insisting he was merely doing a job — and he preferred flying solo, even when crossing German lines.

Unlike other World War I aces like Rickenbacker and Manfred “Red Baron” von Richthofen, Lufbery wasn’t a showman — just a consummate professional. He kept the decorations on his plane neat and understated, never went charging into an attack and always stressed safety first to his young protégés.

Rickenbacker recalled his first flight with Lufbery with some embarrassment. When Rickenbacker landed, fully confident that he hadn’t come across any enemy planes, Lufbery methodically pointed out the bullet holes and shrapnel in Rickenbacker’s plane from the attackers he’d failed to see. Lufbery understood it wasn’t about guts and glory, and that even the best pilots couldn’t be protected by shiny medals or fawning headlines.

It’s impossible to say what happened that afternoon of May 19, 1918. Witnesses suggested Lufbery may have forgotten to buckle his seatbelt in his haste to battle the Germans — or perhaps he removed it to fix a problem with the plane during the air fight. Others thought he leapt from a burning plane. No matter the cause, the tragic result was Lufbery plummeting to his death.

Unlike many World War I soldiers, Lufbery didn’t join up to fight for his country or defend the ideals of freedom and democracy. Instead, he was a man avenging the death of his mentor and close friend, which made him a very different kind of hero.