From Early Records to Pressurized Flight—The Technology and Courage Behind High-Altitude Aviation
The Pioneer Era
Aviation’s earliest altitude pursuits were driven by national prestige. French aviator Roland Garros set successive world records in 1911 and 1912, reaching 18,410 feet. By 1914, Britain’s Norman Channing Spratt surpassed this with 18,900 feet in a modified Royal Aircraft Factory RE.5.
Wartime Necessity
When Germany deployed Zeppelin airships bombing Britain during World War I, the quest for altitude became militarily critical. The airships operated above 20,000 feet, beyond the reach of standard fighter interceptors. British home defence pilots eventually managed to reach the Zeppelins’ altitude and shoot them down beginning in September 1916.
Germany responded with the Rumpler C.VII, a high-altitude reconnaissance aircraft capable of reaching 23,000 feet, with a lightened variant known as the ‘Rubild’ achieving 24,000 feet—putting it beyond Allied fighter range. Rumpler pilots faced extreme challenges: temperatures reaching –30°C and rudimentary oxygen apparatus. Pilot Otto Roosen recalled: “We had the oxygen tube feed into a face mask … You needed the mask to protect your face from the cold. Frostbite happened all the time with the Rumpler. Very dangerous.”
Britain’s equivalent was the Airco DH.4, which served as bomber and reconnaissance aircraft with a 23,000-foot ceiling. Like Rumpler crews, DH.4 pilots wore electrically heated clothing, leather facemasks, and basic oxygen equipment for flights above 16,000 feet.
The Golden Age of Record-Breaking
Peace brought intensified altitude competition among American, European, and Soviet aviators. American test pilots dominated the 1920s. Major Rudolph ‘Shorty’ Schroeder, chief test pilot at the US Army Air Service’s Engineering Division in Dayton, Ohio, secured multiple world records between 1918 and 1920. His final record—33,114 feet on 27 February 1920—nearly proved fatal. Upon changing oxygen flasks at –63°C, moisture on his eyeballs froze, temporarily blinding him. Despite this, he landed safely.
Lieutenant John A. Macready broke Schroeder’s record in 1921, reaching 34,414 feet and earning the first of three prestigious MacKay Trophies. The Engineering Division continued setting records throughout the decade, including the highest altitude by a two-person crew at 37,854 feet in 1928.
These extreme flights revealed severe physiological dangers. Beyond 30,000 feet, hypoxia—oxygen starvation causing blackout and unconsciousness—threatened pilots. Schroeder nearly died when his oxygen supply failed; Macready reported dimmed vision and slowed senses above 30,000 feet.
Solving the Altitude Problem
Three solutions emerged to enable higher altitudes: oxygen masks, pressure suits, and pressurized cockpits.
Oxygen masks proved inadequate above 25,000 feet. Scottish physiologist John Scott Haldane conceived the pressure suit concept in 1920, leading to a prototype fashioned from a rubber diving suit by Siebe Gorman company. However, early pressure suits had significant drawbacks, as RAF physiologist Gerald Marshall noted in 1933: pressure suits were unwieldy, restricted movement, increased respiratory dead space, created unequal pressure across the thorax, and posed fastening challenges.
American aviator Wiley Post, famous for the first solo flight around the world, partnered with B.F. Goodrich in 1934 to develop a practical full pressure suit. The first two prototypes failed—one ruptured from air pressure, another was too restrictive. The third succeeded, though mobility remained limited when inflated with air. On 5 September 1934, Post reached 40,000 feet wearing his experimental suit in his Lockheed Vega ‘Winnie Mae.’ Two months later, he apparently exceeded 50,000 feet, though instruments could not confirm it.
The 1930s belonged to European aviators. Cyril Uwins set a record of 43,976 feet on 16 September 1932 in a modified Vickers Vespa VII. Frenchman Gustave Lemoine surpassed this with 44,808 feet in 1933, followed by Italy’s Renato Donati reaching 47,352 feet in 1934.
Specialized Aircraft and New Heights
In 1936, Britain developed the Bristol Type 138A, an aircraft specifically designed for extreme-altitude flying. RAF Squadron Leader F.R.D. Swain, wearing a full pressure suit with closed-circuit rebreather, reached 49,944 feet on 28 September 1936. During descent, his cockpit windows fogged, his oxygen systems malfunctioned, and the cockpit cover jammed. Swain resorted to cutting open his helmet window with a knife and breathing fresh air until reaching 14,000 feet, where he landed safely.
Eight more records followed with the Type 138A. Flight Lieutenant M.J. Adam achieved the highest—53,937 feet on 30 June 1937—though the flight nearly ended in disaster when cockpit pressure cracked the canopy.
Italian Mario Pezzi broke Adam’s record on 22 October 1938, reaching 56,046 feet in a Caproni 161bis—a record that stood for piston-engine aircraft until the 1990s.
Even with full pressure suits, extreme altitudes imposed severe physical demands. Beyond 35,000 feet, decompression sickness—”the bends”—posed a serious threat, causing gas bubbles in the bloodstream, fatigue, visual disturbance, joint pain, and potentially paralysis or death. Soviet pilot Vladimir Kokkinaki, who reportedly reached 47,806 feet in 1935, stated afterwards: “Though my oxygen apparatus worked perfectly, it is not enough for the stratosphere. A single breath makes one realise this. Every movement requires great effort.”
Pressurization: The Game Changer
Pressurized cockpits and cabins solved these problems by maintaining safe oxygen levels and creating the effect of flying at lower altitudes. This technology enabled sustained flight above 40,000 feet without debilitating physiological effects.
The American USD-9A, a modified British Airco DH.9A, became the first semi-pressurized aircraft in 1921, featuring an airtight chamber with oxygen forced through external turbines. However, fully pressurized experimental aircraft didn’t emerge until several years later. Early examples included Germany’s Junkers Ju 49, France’s Farman F.1001, and the Soviet Chizhevski BOK-1, which first flew in 1936 with a 46,260-foot service ceiling. The technology could prove deadly—on 5 August 1935, Frenchman Marcel Cagnot died when his Farman F.1001 suffered catastrophic decompression.
Commercial and Military Applications
The 1930s saw pressurization technology benefit commercial aviation significantly. The Lockheed XC-35, converted from the Electra Model 10 in 1937, met U.S. War Department requirements for 25,000-foot flight. Belgium’s Renard R.35 was intended as the first commercial pressurized airliner but crashed in 1938. Boeing’s Model 307 Stratoliner made its maiden flight on 31 December 1938, becoming the world’s first pressurized airliner in commercial service, incorporating components from the B-17 bomber.
Britain’s General Aircraft Limited tested pressurization in a modified Monospar ST-25 utility aircraft, designated the GAL 41. On 11 May 1939, it became the first British pressurized aircraft to fly.
As World War II approached, military strategists recognized high-altitude aircraft’s tactical advantage. Pressurized cabins added weight and cost, and enemy fire could cause catastrophic decompression. Nevertheless, Junkers aeronautical engineer Herbert Wagner noted in his 1937 report ‘Construction of High Altitude Aircraft,’ high-altitude bombers could attack from altitudes beyond anti-aircraft gun range and fighter intercept capability.
Wagner argued: “In these great altitudes, at various weather conditions it will be difficult to locate the aeroplane during approach flight by direct sighting or sound detectors. Thus it will be easier for a bomber approaching at high altitude to reach the target undiscovered and attack from a lower altitude.”
The Soviet Union pursued pressure suit development as an alternative. Engineer Yevgeny Chertovsky, who designed the Soviet Union’s first pressure suit in the early 1930s, asserted: “The protection [pressure] suits permit the creation of a stratospheric air force within a very short time. It will constitute a very potent war weapon, since all present ground defences are powerless against it.”
High-altitude reconnaissance also offered strategic advantage. As new monoplane fighters like Germany’s Messerschmitt Bf 109 and Britain’s Spitfire entered service in the late 1930s, standard reconnaissance aircraft became vulnerable. German reconnaissance variants of bombers proved highly vulnerable during the ‘Phoney War’ of 1939-40. High-altitude reconnaissance aircraft, operating beyond fighter range, could photograph targets without detection. Soviet military physician Vladislav Spasskiy noted in the mid-1930s: “Aviation reconnaissance by an aggressor armed with the latest equipment can secretly reconnoitre the territories of a future adversary from great altitudes – even in peacetime.”
By the war’s outbreak, Nazi Germany had achieved decisive superiority in high-altitude military aviation, deploying pressurized reconnaissance aircraft exceeding 40,000 feet operationally, ushering in a new era of stratospheric warfare.
This article is from the book “Combat in the Stratosphere: Extreme Altitude Aircraft in Action During WW2” by Steven Taylor, available here.
