Wop May, Vic Horner, and the Forty-Below Mercy Flight That Carried Diphtheria Antitoxin to Fort Vermilion

On January 2, 1929, two Edmonton pilots flew diphtheria antitoxin several hundred miles north to Fort Vermilion, Alberta in temperatures of forty below zero - carrying the medicine inside their own coats to keep it from freezing. Wilfrid Reid “Wop” May and Vic Horner made the flight in open-cockpit biplanes with no weather protection, no radio communication, and no guarantee of survival. The children of Fort Vermilion survived. The flight permanently changed how Canada understood what an airplane was for.

Who Was Wop May?

Wilfrid Reid May, known universally as “Wop,” entered aviation history twice: first over the Western Front, then over the Canadian North.

On April 21, 1918, May was flying his first combat patrol when Manfred von Richthofen - the Red Baron, with 80 confirmed kills and a blood-red Fokker Triplane - broke from the main engagement to pursue the 21-year-old Edmonton pilot personally. May had been warned before takeoff: don’t chase stragglers, don’t leave the formation. He’d broken both rules within fifteen minutes.

What followed was not a skilled escape. May dove, twisted, and threw his aircraft around the sky on pure instinct. Roy Brown, a Canadian pilot flying a Sopwith Camel, saw what was happening from above and drove a burst of rounds into the triplane. Richthofen went down over the Somme.

Historians have argued for a century whether it was Brown’s fire or Australian ground fire that killed the Red Baron. The debate continues. What is not debated: May flew home. Richthofen did not.

From the Western Front to the Canadian Bush

After the armistice, May returned to Edmonton and, with his brother Court, built a small aviation operation - mail runs, charter flights, small contracts to places that needed someone to go there. By the late 1920s, he was among the most experienced bush pilots working in the Canadian North.

The North in 1929 was not a place with infrastructure. Vast stretches of spruce forest and muskeg connected isolated communities along the Peace and Mackenzie river systems. In summer, those communities traveled by water. In winter, by dogsled. There were no roads worth the name, no weather forecasting, no radio in most places - just a telegraph line that ended somewhere south of wherever you needed to go.

Aircraft of that era were not sophisticated machines. Open cockpits. Engines that required fire pots underneath them for an hour before they’d turn over in deep cold. Navigation by compass, paper map, and memorized landmarks. You didn’t file an instrument flight plan. You looked at the sky, made a judgment, and went. If you went down in the wrong place, rescue meant days or weeks of dogsled teams working through country that didn’t forgive mistakes.

Bush flying in this context was not sport. It was the supply chain. It got medicine, mail, and gear to places that had no other way to receive them.

The Diphtheria Outbreak at Fort Vermilion

In January 1929, a diphtheria outbreak struck Fort Vermilion, Alberta - a small community several hundred miles north of Edmonton, well above the sixtieth parallel. The local doctor was watching children fall ill. Without antitoxin, he knew exactly where this was going.

The telegram came south. Edmonton had the medicine. The only question was delivery.

By the fastest dogsleds available, covering that distance in that weather would take weeks. Diphtheria does not negotiate with logistics. Dogsled was not an option that arrived in time. Flying was.

The Problem of Flying Medicine at Forty Below

On paper, the flight was not a reasonable plan. The open-cockpit biplane May was flying offered roughly the weather protection of a motorcycle. At eighty to eighty-five miles per hour, ground temperatures of forty below zero translated into windchill conditions that challenge the human body’s ability to keep functioning. Pilots of that era managed extreme cold through layers, fur-lined helmets, goggles, and hard-won experience - but for limited periods. This would not be a limited period.

The medicine itself was a separate problem. Antitoxin is biological material with a viable temperature range. It cannot freeze. In an open cockpit at forty below, keeping anything above freezing requires active intervention.

May and Horner’s solution was simple and direct: carry the antitoxin inside their own coats, against their own bodies. Their body heat would be the medicine’s warmth source. They would be uncomfortable. The medicine would survive.

The Flight North

May and Horner left Edmonton on January 2, 1929.

They flew north over the frozen Peace River, over stands of black spruce pushing through the snow, past occasional smudges of smoke from scattered settlements. Navigation was by landmark, compass, and dead reckoning across an enormous cold silence. The goggle lenses frosted over, thawed from the heat of their eyes, and frosted again. The antitoxin was warm against May’s chest.

They stopped at McLennan to refuel. Ground time was kept as short as possible - engines allowed to cool in those temperatures risked not restarting. Then north again.

The Peace River country gets quieter as you fly into it. The distance between communities stretches. The world empties out. The cold at those latitudes is not a weather event; it is a permanent condition, old and indifferent to schedules.

May and Horner each understood they were spending a warmth budget that had limits. They also understood exactly what was at the other end of the flight: specific children, in a specific place, with a specific disease that the tin inside May’s coat would stop. That specificity changes the calculation. You make different decisions when you know exactly what depends on you arriving.

Arrival at Fort Vermilion

They made Fort Vermilion.

The doctor was at the field when they landed. The antitoxin was handed over still warm from the pilot’s body. Treatment began. The children survived.

Why This Flight Still Matters

The Fort Vermilion mercy flight was not the last time May flew toward something that needed him. He went on to help build the infrastructure of commercial aviation in northern Canada - organizing operations, lobbying for air services, training pilots, working on the foundational problem of connecting isolated communities reliably to the outside world. He and his generation turned bush flying from a series of individual adventures into something that functioned as a system.

Wop May died in Edmonton in 1952 at the age of 55 - a heart attack, not an aircraft accident - after a career that should have ended over the Somme in 1918, and that found its highest purpose in a January flight over the Peace River country.

Vic Horner kept flying too. That generation mostly did. The job was what they knew. The job was the point.

What Fort Vermilion proved, in a way that could not be argued with afterward, is that the airplane was infrastructure - not a novelty, not a demonstration of daring, but the only form of infrastructure capable of crossing that distance in that season in time that mattered. Before the mercy flight, you could call bush aviation a novelty. After Fort Vermilion, you could not say that with a straight face.

Much of what northern aviation is today - the understanding that the airplane serves the people below it, that weather does not automatically determine whether a flight gets made - traces back to flights like this one. Two men doing the uncomfortable math of their own body heat against a January horizon, deciding the math came out in favor of going.

Key Takeaways

• January 2, 1929: Wop May and Vic Horner flew diphtheria antitoxin from Edmonton to Fort Vermilion, Alberta in open-cockpit aircraft at 40 below zero, saving children in an isolated northern community.
• May was already a figure of historical record before the mercy flight - on April 21, 1918, he survived being personally targeted by the Red Baron (Manfred von Richthofen, 80 confirmed kills) during his very first combat mission.
• With no viable temperature control available in their aircraft, May and Horner kept the antitoxin from freezing by carrying it inside their own coats, against their bodies, for the entire flight.
• A refueling stop at McLennan was the only ground time taken; extended stops in those temperatures risked engines that would not restart.
• The Fort Vermilion flight established, in practical and public terms, that bush aviation was not a sport but essential infrastructure - a legacy that shaped northern Canadian aviation for generations.