At 10:43 on 7 December 1936, a radio operator somewhere over the South Atlantic tapped out a short line of Morse from the flying boat Croix-du-Sud: “Coupons moteur arrière droit” – cutting the rear starboard engine. Then the signal stopped. No wreck, no bodies and no further word ever came back.

At the controls was Jean Mermoz, the most famous airline pilot in France. Across a decade he had been held captive in the Sahara, stranded high in the Andes and had carried the first all-air mail across the South Atlantic. France knew him as l’Archange, the Archangel.

His story is the story of the Aéropostale, the French mail line that set out to link Toulouse with Dakar and South America by air, and which, according to the French Air Force’s own history centre, lost at least one pilot a month in its harsh early days.

From Syria to the Line

Mermoz signed up for military aviation in 1920, failed his first attempts at the pilot’s licence and finally earned it in early 1921. Posted to Syria, he survived a forced landing in the desert that ended in a days-long march back to safety. By 1924 he was out of uniform, broke and taking odd jobs in Paris.

Rescue came from Toulouse. Didier Daurat, who ran operations for Pierre-Georges Latécoère’s airline, gave him a test flight in autumn 1924. Mermoz showed off with aerobatics, was scolded for it and flew a sober circuit instead. He started, like every new pilot on the Line, in the workshop, then flew Breguet 14s over the Pyrenees between Toulouse and Barcelona.

In late 1925 the Aéro-Club de France gave him its medal for the French pilot who had flown the most kilometres that year: 120,000 km in 800 hours.

Prisoner of the Sahara

In 1926 Mermoz moved to the Casablanca–Dakar sector, the most dangerous stretch of the route. On 22 May his engine failed and he put down on the coast in unsubdued territory with his interpreter. After walking through a sandstorm toward Cap Juby, the pair were taken prisoner by Moorish tribesmen. Mermoz was released at Cap Juby for a ransom of 1,000 pesetas.

Cap Juby would soon be run by another Latécoère pilot, Antoine de Saint-Exupéry. The other name that runs through Mermoz’s career is Henri Guillaumet, a friend from his air force days whom Mermoz had persuaded to join Latécoère in 1925. The three would become the best-known pilots of the Line.

Arte’s documentary on the Latécoère lines and the Aéropostale, shared by the Latécoère Foundation.

Night Mail and the Andes

On 10–11 October 1927, Mermoz and Élisée Négrin flew non-stop from Toulouse to Saint-Louis in Senegal in a Latécoère 26, a 4,270 km leg. A hoped-for continuation across the ocean ended when the propeller broke on landing.

Weeks later the company, now the Compagnie générale aéropostale, sent him to South America as chief pilot. In April 1928 he flew the first night mail between Rio de Janeiro and Buenos Aires, and night flying became his weapon against the steamships.

Then came the Andes. In early March 1929 he carried the Comte Henry de La Vaulx, president of the Fédération Aéronautique Internationale, over the cordillera to Chile in a Latécoère 25, with mechanic Alexandre Collenot. On the way back, without the count, violent air currents pinned the aircraft to the ground for an emergency landing at about 4,200 m. The two men spent days repairing it, launched it down a precipice to gain flying speed and glided into Copiapó when the radiator hoses failed again. On 15 July 1929 Mermoz and Guillaumet opened the regular Buenos Aires–Mendoza–Santiago service, partly flown on the Potez 25.

21 Hours to Natal

One gap remained. Between Africa and South America the mail still went by ship, taking four days. French rules banned landplanes from commercial ocean crossings, so the Aéropostale fitted a Latécoère 28 with floats. Mermoz qualified as a seaplane pilot and, with navigator Jean Dabry and radio operator Léopold Gimié, set closed-circuit world records for seaplanes in April 1930.

On 12 May 1930 the red Latécoère 28.3 Comte-de-la-Vaulx, named after the count who had died in an air crash in New Jersey, lifted off near Saint-Louis. On board, according to AFP, were 130 kg of mail. At dusk the crew met the “pot au noir”, the stormy doldrums of the intertropical convergence zone.

He threaded the floatplane through at about 50 m above the waves. After 21 hours and 10 minutes the Comte-de-la-Vaulx settled on the Potengi river at Natal on 13 May. The mail was transferred to another aircraft for Rio, Montevideo, Buenos Aires and Santiago. For the first time, a letter had crossed the South Atlantic entirely by air.

Getting home was harder. The heavy floatplane failed to get off the water 52 times. When it finally lifted in July, an oil leak forced Mermoz to ditch roughly 900 km off the African coast. The aviso Phocée rescued the crew and the mail, but the Comte-de-la-Vaulx sank while under tow.

Weeks later, testing a modified Laté 28 for the North Atlantic, the aircraft broke up around him over Capens, south of Toulouse. He got out of the wreckage and survived on a torn parachute.

France 3 Occitanie’s “Histoires du ciel” archive: interviews with navigator Jean Dabry and with Mermoz’s mother.

The Archangel and His Machines

The Aéropostale went into liquidation in 1931 and was folded into the new Air France in 1933. Mermoz kept pushing for landplanes over the ocean. In January 1933 he crossed the South Atlantic in René Couzinet’s trimotor Couzinet 70 Arc-en-Ciel, and from 1934 he flew the four-engined Latécoère 300 flying boat on the route, and served as Air France’s inspector general.

He also grew openly critical of the aircraft he was asked to fly. On 10 February 1936 his long-time mechanic Collenot was lost with the whole crew of the Latécoère 301 Ville-de-Buenos-Aires. In politics he drifted to the nationalist right, joining the Croix-de-Feu and becoming vice-president of the Parti social français in 1936.

The Last Crossing

On the morning of 7 December 1936 the Croix-du-Sud, registration F-AKGF, left Dakar for Natal. It soon turned back with trouble on the rear starboard engine, whose propeller would not go into coarse pitch. Rather than wait for a replacement aircraft and delay the mail, Mermoz took off again after a quick repair.

About four hours later came the message about the rear starboard engine, and then silence. With Mermoz were co-pilot Alexandre Pichodou, navigator Henri Ézan, radio operator Edgar Cruveilher and mechanic Jean Lavidalie. Searches found nothing.

The most widely cited theory is that the reduction gear on the repaired rear engine failed and the propeller tore loose, damaging the tail or the control runs behind it. A Uruguayan parliamentary commission alleged sabotage in 1941, but no evidence has ever supported that claim.

On 13 December, Mermoz and the entire crew were cited in the order of the Nation at the request of Léon Blum’s government.

The citation records that he was on his 24th crossing of the Atlantic, on the postal line he had been the first to trace.

What the Archangel Left Behind

Mermoz logged 8,200 flying hours. Within weeks of his loss, Maryse Bastié flew the South Atlantic solo in an aircraft named after him. Joseph Kessel published his biography Mermoz in 1938, and Jean Bugatti named the Bugatti Atlantic in his honour.

His name is now on streets, schools and a neighbourhood of Dakar, on a peak of the Fitz Roy massif in Patagonia, and in Jean-Jacques Annaud’s 1995 IMAX film Wings of Courage, where Val Kilmer played him alongside Craig Sheffer as Guillaumet and Tom Hulce as Saint-Exupéry.

Archive footage of the Latécoère 300 Croix-du-Sud arriving at Les Mureaux, France, in February 1934 after a 20,000 km trip.

Airliners now cross the same ocean in a few hours, far above the pot au noir. Mermoz flew through it at 50 m, at night, by full moon, so that a letter could reach Santiago a few days sooner.

Sources: French Wikipedia (Jean Mermoz), English Wikipedia (Jean Mermoz), L’Envol des Pionniers (Jean Mermoz chronology), IRSEM/CReA “7 décembre 1936: Mermoz”, AFP