The rise to power of various totalitarian nations in the 1930s, such as Japan, Italy and Germany, convinced the senior political and military leadership of the United States that the nation would eventually be drawn again into overseas conflicts. They therefore sought to prepare the country’s military forces for that undertaking.
In the forefront of building up the strength of the United States armed forces was President Franklin D. Roosevelt. A former Secretary of the Navy, Roosevelt initially favoured the funding of the US navy, long considered the guardian of America’s shores. However, he also began to seek funding from Congress for increasing the size and strength of the US army and, by default, the Air Corps.
In January 1939, Roosevelt asked Congress to expand the Air Corps from its existing inventory of 800 aircraft to a force of 5,500 planes. By way of comparison, the German Air Force had 4,100 planes in service in January 1939. In April 1939, Roosevelt signed the National Defense Act to increase military spending the following year, authorizing 6,000 aircraft for the Air Corps.
When a senior Air Corps general asked Congress in June 1940 for 18,000 planes by April 1942, Roosevelt quickly approved the request. In May 1940, Roosevelt called for 50,000 aircraft per year to be built by American industry. The US Army Air Corps was renamed the ‘US Army Air Forces’ (USAAF) in June 1941.
The B-17 bomber at war
Although originally sold to Congress as a defensive coastal patrol bomber, the Air Corps classified the B-17 as an offensive ‘heavy bomber’ at the beginning of the Second World War on the basis of its weight. It was meant for the strategic bombing role. All aircraft listed as heavy bombers were intended to accurately drop bombs from high altitudes, classified as 15,000 feet and above at the time.
The first model of the four-engine B-17 to see combat was the B-17C but with the Royal Air Force (RAF) and not the USAAF. Thirty-eight had been originally ordered by the latter but due to the desperate straits faced by England at the time, twenty slightly modified units were given to the RAF. The RAF designated them the Fortress Mk. I but did not think much of them.
Boeing soon upgraded the eighteen units of the B-17C delivered to the Air Corps to the improved B-17D configuration. The firm also built forty-two brand-new units of the B-17D for the USAAF. Lessons learned from the B-17D resulted in the building of 512 units of an up-gunned variant referred to as the B-17E, of which the RAF received forty-five. The latter labelled them as the ‘Fortress IIA’.
The B-17 Flying Fortress, including the ‘D’ and ‘E’ versions, first saw combat with the USAAF in the Pacific Theater of Operations (PTO) following Pearl Harbor. It was envisioned that they would be employed in attacking enemy ships. However, they did not have much success in that role and were withdrawn from that theatre in September 1943.
It was while flying over Western Europe during daylight hours in the strategic bombing role that the B-17 Flying Fortress found its true calling. The first combat mission flown over Western Europe by the USAAF occurred in August 1942 with the B-17E version.
The ‘E’ model of the B-17 Flying Fortress was replaced in turn by progressively improved models labelled the ‘F’ and ‘G’ variants. A total of 3,405 units of the ‘F’ model were built and 8,680 units of the ‘G’ model.
By the time production of the B-17 Flying Fortress was completed, 12,276 units had rolled off a number of different companies’ assembly lines as Boeing could not build all those ordered by the USAAF. Wartime losses of B-17 Flying Fortress to all causes, combat and non-combat, are listed as 4,754 aircraft.
Other four-engine bombers
Besides the Boeing B-17 Flying Fortress, the USAAF employed two other four-engine bombers during the Second World War. The first was the Consolidated Aircraft Company’s B-24, labelled as a heavy bomber and named the ‘Liberator’. The other was the Boeing B-29, named the ‘Superfortress’. Due to its weight, the USAAF labelled the B-29 as a ‘very heavy bomber’.
Of these two four-engine bombers, the first to enter service with the USAAF was the B-24 Liberator. Nine units of a model designated the B-24A showed up in service in the summer of 1941. However, these were employed as transport aircraft rather than bombers.
The ‘A’ model of the B-24 Liberator was followed by a long line of progressively improved models, labelled the ‘C’ through ‘M’ variants. The most-produced model of the bomber was the ‘J’, with 6,678 units constructed. In descending numbers there were 3,100 units of the ‘H’ built and 2,593 units of the ‘M’ version.
By the time production of the B-24 Liberator ceased, approximately 18,400 units had rolled off the assembly lines, making it the most numerous American aircraft of all types built during the Second World War. Losses of B-24 Liberators to all wartime causes are listed as 2,112 aircraft.
The bigger the better
The Boeing B-29 Superfortress very heavy bomber was based on the firm’s development of the B-17 Flying Fortress, as well as some of its experimental four-engine aircraft. The Air Corps first expressed interest in the Boeing proposal for a state-of-the-art bomber in November 1939. The USAAF saw it as the eventual replacement for the B-17 Flying Fortress and B-24 Liberator series
The first example of the B-29 Superfortress flew in September 1942. Due to the complexity of the aircraft’s design and it being rushed into production, it was saddled with an endless number of both major and minor design issues, the resolution of which delayed the introduction of the aircraft into operational service. One of the biggest design issues was the unreliability of its four large engines, which would plague the aircraft throughout the Second World War.
As Boeing continued to work the bugs out of the Superfortress, the USAAF made the decision in December 1943 that when series production of the aircraft commenced, it would be reserved for service in the PTO where its long range was of key importance.
The Superfortress began flying missions over Japan during the last two months of 1944 and continued to do so until the Japanese surrender in September 1945. It was the two atomic bombs dropped on Japan in August 1945 by B-29 Superfortresses that helped to push the Japanese government to the surrender table.
There were three models of the B-29 Superfortress that saw combat: these included 2,513 units of the original B-29, followed by 1,119 units of the B-29A and 311 units of the B-29B. Wartime losses of the Superfortress to all causes are listed as 414 aircraft.
B-29 back-up
When the B-29 Superfortress was ordered from Boeing, the Air Corps took no chances on the bomber being a failure in service. As a result, they ordered at the same time a similar four-engine very heavy bomber from Consolidated. It was designated the B-32 and named the ‘Dominator’.
Due to numerous design problems, the first fifteen production units of the B-32 Dominator did not enter service with the USAAF until November 1944. They would see some limited combat action during the last few months of the war in the PTO.
In total, 115 units of the Dominator were built before the production contract was cancelled upon the end of the conflict and all those built were soon pulled from service. Following the Second World War, all the B-32 Dominators were quickly scrapped.
Twin-engine medium bombers
The USAAF employed two different types of twin-engine medium bombers during the Second World War, in both strategic and tactical bombing roles. These were the North American B-25 and the Martin B-26. Both entered the Air Corps’ inventory in February 1941. The B-25 was named the ‘Mitchell’ and the B-26 the ‘Marauder’. Both would see their first combat missions with the USAAF in April 1942
The USAAF definition of medium altitude was 7,500 to 15,000 feet. As the war went on, some B-25s were configured as low-level light tactical attack aircraft. In that role they were armed with a variety of forward-firing weapons including cannons and machine guns. These were for strafing Japanese ships and ground facilities. The USAAF defined low altitude as 1,000 to 7,500 feet.
A total of 9,816 units of the B-25 Mitchell were built. Only 5,288 units of the B-26 Marauder rolled off the assembly line as it was the more costly of the two aircraft. Both came in several variants, with the final model of the Mitchell – the B-25J – being the most numerous with 4,318 units completed. With the B-26 Marauder, the most numerous model was the B-26B with 1,883 units being constructed. The last B-25 Mitchell was pulled from USAF service in 1960. All the B-26 Marauders had disappeared from service by 1947.
Ground-attack bombers
Inspired by German and Russian employment of twin-engine light attack bombers during the Spanish Civil War (1936–39), in 1938 the Air Corps decided that they wanted the same. The first aircraft that met the Air Corps’ specifications was the Douglas A-20 series, with the initial 143 units entering service in November 1940. This aircraft was named the ‘Havoc’.
By September 1944, a total of 7,098 units of the A-20 Havoc had been built in different versions, the bulk of them being diverted to Lend-Lease. The Air Corps/USAAF employed approximately 1,700 units of the A-20 Havoc series during the Second World War.
At the same time as the Air Corps was testing the prototype A-20 Havoc, it was expressing a great deal of interest in eventually replacing it with a far superior Douglas twin-engine light attack bomber then on the drawing board. That aircraft would eventually enter the USAAF inventory as the A-26 and was named the ‘Invader’.
The USAAF ordered 500 units of the ‘B’ model of the A-26 Invader in October 1941. Unfortunately, production bottlenecks meant that it would not see its first combat until June 1944. The ‘B’ model was followed into service by the ‘C’ model. During its time in service, a total of sixty-seven units of the A-26 Invader were shot down. It is credited with seven aerial victories during the Second World War.
All told, 2,452 units of the Invader were constructed before the production contract was cancelled upon the end of the Second World War. In 1948 the A-26 Invader was relabelled as the B-26 Invader, which has long created confusion with the B-26 Marauder that was pulled from USAF service in 1947. The B-26 Invader would go on to see combat during both the Korean and Vietnam wars.
Lend-Lease
Lend-Lease, an American armament programme begun while the country was still neutral, provided American goods ranging from food to aircraft to ships at no cost to friendly foreign governments. In return, the United States was granted leases to bases in these foreign countries. President Roosevelt signed the Lend-Lease Act into law on 11 March 1941. The programme ended in September 1945.
The first new fighter
Most of the pursuit monoplanes employed by the USAAF during the Second World War appeared in service prior to America’s official entry into the conflict in December 1941. The first was the Curtiss P-40, assigned the name ‘Warhawk’. Some 524 units were ordered in 1939, making it the largest number of Army Air Corps planes contracted for up to that time. It was developed from the Curtiss P-36 fighter.
The initial delivery of the P-40 Warhawk to the Air Corps took place in 1940. It was followed into service by a number of progressively improved versions, from the P-40B through P-40N. Envisioned as a fighter-bomber and not as an air-superiority fighter, it was somewhat obsolete before it entered service. The Air Corps was forced to use the P-40 Warhawk as an air-superiority fighter in 1942 and into 1943 because it was available in the numbers required when America entered the war.
By the time the P-40 Warhawk production lines came to a halt in 1944, more than 14,000 units of the aircraft had been built, making it the third most-produced American pursuit plane of the Second World War.
At its peak, the USAAF had only 2,499 units of the P-40 Warhawk in service in April 1944. By the time the war ended, only one USAAF squadron was still flying the Warhawk. It did much better when engaging Japanese fighters than German fighters, whose pilots did not think much of the aircraft.
Total combat losses of the P-40 Warhawk flying with the USAAF came in at 533 aircraft. It was credited with 481 kills in the air-to-air arena and the destruction of forty enemy aircraft on the ground. The USAAF’s top-scoring P-40 Warhawk ace during the Second World War was Bruce Keener Holloway, who accounted for thirteen Japanese planes and eventually rose to the rank of general after the war.
Most of the P-40 Warhawk planes built would fly with friendly foreign countries such as the Soviet Union or Great Britain, having been provided under Lend-Lease. In service with the RAF, the Warhawk was assigned the name ‘Tomahawk’ or ‘Kittyhawk’, depending on the version employed.
Not up to the job
The P-40 Warhawk was followed into production by the Bell Aircraft Corporation P-39 Airacobra. The Air Corps placed an initial order for eighty units of the aircraft in October 1939, designated the P-39C, with deliveries commencing in January 1941. Having been subjected to conflicting design requirements by the Air Corps during its development phase, the Airacobra proved poorly suited to the role of air-superiority fighter in the eyes of the USAAF.
As soon as more capable air-superiority aircraft entered the USAAF inventory in sufficient numbers, the P-39 Airacobra was reserved for the fighter-bomber role or for training duties. In service with the USAAF, 107 units of the aircraft were lost in combat during the Second World War.
Reflecting the USAAF’s general disdain for the P-39 Airacobra, the majority of the aircraft’s production run of 9,585 units was assigned to Lend-Lease. The Airacobra disappeared from USAAF service upon the conclusion of the conflict.
Twin-engine fighter
In 1937, the Air Corps had secretly asked a number of American aviation firms to take part in a competition to design a fighter-interceptor aimed at taking on enemy bombers. The winning design for this job was submitted by the Lockheed Aircraft Company, with a twin-engine plane referred to as the P-38 and named the ‘Lightning’.
Initial models of the P-38 Lightning to enter Air Corps’ service included twenty-nine units of the original P-38 version, ordered in September 1939, with deliveries commencing in June 1941. They were followed into the Air Corps’ inventory by thirty-six units of the P-38D beginning in August 1941. In November 1941, the first of 210 units of the P-38E began appearing in front-line service with the Air Corps.
The first three versions of the P-38 Lightning were plagued by unforeseen design issues. The first combat-ready model of the P-38 Lightning was considered the P-38F, which did not begin entering service until March 1942. Follow-on models of the Lightning would include the P-38G through to the P-38L.
However, German fighters proved superior to the P-38 Lightning and resulted in it being replaced by newer-generation USAAF fighters in the European Theatre of Operation (ETO) by 1944. It did much better in the PTO when confronted by less capable Japanese fighters. Major Richard I. Bong of the USAAF downed forty Japanese planes while flying in a P-38 Lightning, becoming America’s top-scoring ace of the Second World War.
When the production lines for the P-38 Lightning were finally closed, a total of over 10,000 units had been assembled. Approximately 1,400 units, either built new or converted from existing fighter models, were configured as photo-reconnaissance aircraft.
Towards the end of the Second World War, seventy-five units of the P-38L Lightning were converted into radar-equipped night-fighters. In this new role they were re-designated as the P-38M Lightning. Deployed in the PTO in the last few months of the war, they never engaged any enemy aircraft in combat.
Combat losses for the P-38 Lightning are listed at 1,758 units. It was responsible for downing 1,771 enemy aircraft in air-to-air combat (mostly Japanese), and destroying another 749 on the ground. The Lightning would continue in American military service until 1949.
Foreign fighters in USAAF service
The initial plans for the first USAAF units deployed to Great Britain in 1942 included fighter groups equipped with the Lockheed P-38 Lightning and the Bell P-39 Airacobra. A ‘group’ was the primary combat unit of the USAAF and normally comprised three to four squadrons flying the same aircraft.
Because the P-39 Airacobra lacked the performance to go up against German fighters it was decided that the first three USAAF fighter groups to fly from Great Britain in combat were to be equipped with the Spitfire Mk. V. This was a British-designed and built plane from Supermarine Aviation Works, a subsidiary of Vickers-Armstrong. The first model of the Spitfire entered RAF service in 1938.
Of the three USAAF fighter groups equipped with various versions of the Spitfire, the one that remained in Great Britain converted to a newer American-designed and built fighter in March 1943. The other two groups would continue flying the Spitfire until early 1944. In total, the USAAF would take into service approximately 600 Spitfires during the Second World War.
The most-produced fighter
Successful aircraft often require a certain gestation period before evolving into their most efficient form. Such was the case with the Republic Aviation Corporation’s P-47 pursuit plane, named the ‘Thunderbolt’. Republic had formerly been the Seversky Aircraft Corporation, the designers and builders of the P-35 pursuit plane.
Building on the P-35, Republic came up with the P-43 pursuit plane, named the ‘Lancer’. It did not live up to the Air Corps’ expectations but was ordered anyway to keep the firm’s production line open for the hopefully more successful follow-on, the P-47 Thunderbolt, which would not be ready to enter into production until the spring of 1942.
The first production model of the P-47 Thunderbolt was designated the P-47B. Some 107 of these had been ordered by the Air Corps in September 1940, with deliveries beginning in March 1942. At the same time that the P-47B Thunderbolt model was ordered, another order went out for 602 units of a faster P-47C Thunderbolt variant.
The first units of the P-47C Thunderbolt were delivered to the USAAF in September 1942. On the heels of the ‘C’ model came the ‘D’ and ‘N’ variants. The P-47D Thunderbolt was the most numerous model of the series, with 12,602 units being constructed. The P-47N Thunderbolt was a specially-designed longer-range version intended to escort B-29 bombers in the PTO, with 1,816 units built.
The P-47 Thunderbolt destroyed 3,082 enemy aircraft in air-to-air combat, with another 3,202 on the ground. The top-scoring USAAF ace in the ETO was Colonel Francis S. Gabreski who, flying the P-47 Thunderbolt, is credited with downing twenty-eight enemy aircraft in air-to-air combat and destroying another three on the ground.
Originally intended as a lightweight interceptor of enemy bombers, the P-47 Thunderbolt eventually evolved into one of the largest and heaviest prop-driven fighters ever built. Upon arrival in England, it took on the role of bomber escort until replaced by a more capable and longer-range air-superiority fighter. It then became the main USAAF fighter-bomber in the ETO.
By the time production of the P-47 Thunderbolt was wrapped up at the end of the Second World War, a total of 15,683 units had been built, making it the most numerous pursuit aircraft constructed by American factories during the conflict. The P-47 Thunderbolt combat losses are listed at 3,077 units. It would remain in American military service until 1953 but would not see combat during the Korean War.
The best all-round fighter
The USAAF had decided early on that the main pursuit plane for the war effort was going to be the P-47 Thunderbolt. However, a senior USAAF leader remained flexible enough to consider another aircraft that demonstrated a superior level of performance over the Thunderbolt. That aircraft was the P-51B, named the ‘Mustang’.
The P-51B Mustang was designed and built by North American Aviation. It first flew in May 1943. So superior was it over the P-47 Thunderbolt that it quickly replaced it in the bomber-escort and air-superiority role in the skies over the ETO by the end of 1943. A total of 1,988 units of the ‘B’ model of the P-51 Mustang were constructed.
The P-51B Mustang was joined by the P-51C of which 1,750 were ordered. The ‘C’ model was a near-identical version of the ‘B’ model but built at a different factory. The ‘B’ and ‘C’ versions of the P-51 Mustang were replaced on the production line by the progressively-improved ‘D’ model, of which 7,965 units were built.
Follow-on models of the P-51 Mustang included 555 units of the taller-tailed P-51H, which was a lightened version of the aircraft to boost performance. There were also 1,500 units built of the ‘K’ model, which was a near-identical copy of the P-51D variant but built at a different factory.
By the time production of the P-51 Mustang ceased in 1945, a total of 15,367 units had been delivered to the USAAF. Of that number, 2,520 units were lost in combat, more to enemy ground fire than to air-to-air combat. In return, the P-51 Mustang downed 4,950 enemy planes in air-to-air combat and destroyed another 4,131 on the ground.
The USAAF top P-51 Mustang ace in the Second World War was Major George Preddy who accounted for twenty-six enemy aircraft in the ETO before he was shot down and killed by US army anti-aircraft fire in December 1944 in a friendly-fire incident.
The P-51 Mustang would last in post-war American military service until 1956. In 1948, the letter ‘P’ for pursuit plane was dropped and the P-51 Mustang became the F-51 Mustang, ‘F’ standing for fighter. The F-51D Mustang would see use during the Korean War.
How it came to be
The P-51 Mustang came into service with the USAAF by a very convoluted path. The original model of the aircraft was not ordered by the Air Corps but by the British government from American industry as the NA-73X in 1940. Upon delivery of the first examples in November 1941, which the RAF designated the Mustang IA, the RAF decided it was the best American fighter they had seen but felt it performed poorly at medium and high altitudes due to its underpowered American-designed and built engine.
In October 1942, the RAF had five units of the Mustang IA fitted with the same British-designed and built Rolls-Royce Merlin engine that powered their Spitfire fighter. The USAAF picked up on the merits of this combination of design features and this is what resulted in the production of the P-51B Mustang which was fitted with an American-built copy of the British engine.
Prior to ordering the P-51B, the USAAF had held back fifty planes from a British contract for 150 units of the Mustang II, following the Japanese attack on Pearl Harbor. In USAAF service, this model of the P-51 Mustang was designated as the P-51A. It first flew in February 1943 and entered operational service with the USAAF the following month.
The P-51A Mustang was employed as a fighter in the China/Burma/India (CBI) Theatre. In the ETO, the American engine made it unsuitable as a high-altitude fighter, so it was employed as a photo-reconnaissance aircraft.
Originally, the USAAF wanted to order 1,200 units of the P-51A but the advent of the far superior ‘B’ model of the aircraft resulted in the order being cut down to 320 units of the ‘A’ model in August 1942. Fifty units were transferred to the RAF in return for those held back by the USAAF from the RAF’s original order.
Night-fighter
The only dedicated night-fighter to enter service with the USAAF during the Second World War was designated the P-61 and named the ‘Black Widow’. Designed and built by Northrop Aircraft Inc., the initial version of the twin-engine interceptor, labelled the P-61A, was ordered in September 1941 but the first deliveries were not made until October 1943 due to technical design issues with the aircraft
The radar-equipped P-61A Black Widow was followed into service by 450 units of the P-61B model, with the first showing up in front-line service in August 1944. Prior to the introduction of the P-61 Black Widow, some USAAF units employed the British-designed and built Bristol Beaufighter twin-engine night-fighter. Other USAAF night-fighter units used the Douglas P-70 interim night-fighter, a variant of the Douglas A-20 Havoc light attack bomber.
The final variant of the P-61 Black Widow was the ‘C’ model, of which 517 were ordered but only forty-one entered service before cancellation of production at the conclusion of the Second World War.
Twenty-five of the P-61 Black Widow would be lost to non-combat causes during the Second World War. None were destroyed in combat by enemy action. The aircraft was credited with shooting down fifty-eight enemy planes during the conflict.
The P-61 Black Widow lasted in post-war American military service until 1954. It was one of the first fighter-interceptors tasked with guarding the United States from attack by Soviet long-range bombers upon the beginning of the Cold War in 1947.
The first jet-powered fighter
In the early part of 1943, the USAAF became aware of German development of the Messerschmitt Me 262, the world’s first subsonic (below the speed of sound) jet fighter. The USAAF quickly tasked American industry to come up with a subsonic air-superiority jet fighter of its own. The end result was the delivery of the first of 563 units of the Lockheed P-80A in February 1945. The aircraft was named the ‘Shooting Star’.
Only four prototypes of the P-80 Shooting Star made it overseas before the conclusion of the Second World War. None of the early production examples of the P-80A Shooting Star made it overseas before the war ended, despite the best efforts of the USAAF.
The only Allied jet fighter to see combat during the Second World War was the RAF subsonic Gloster Meteor I, which entered operational service on 12 July 1944, a few days after the German Me 262 had with the German Air Force.
Dive-bombers
The successful German employment of a single-engine dive-bomber known as the ‘Ju-87 Stuka’ during the early part of the Second World War (1939–40) caused the Air Corps to seek out such a dedicated ground-attack aircraft. Several were taken into service before it was decided that existing air-superiority fighters could perform that role without the need for specialized dive-bombers.
Among the Air Corps/USAAF dive-bombers taken into service were 875 units of various versions of a Douglas-designed and built US navy dive-bomber named the ‘Dauntless’. In Air Corps/USAAF service the plane was designated the A-24, with only a small number ever seeing combat before being pulled from front-line service.
A cancelled French government contract for 2,330 units of a dive-bomber designed and built by the American firm of Vultee was picked up by the RAF who named the aircraft the ‘Vengeance’. Out of that number the Air Corps/USAAF retained 140 units that they labelled the A-32. None saw combat and all were quickly relegated to non-combat roles.
The only dive-bomber to see extensive combat service with the USAAF was designated the A-36A and named the ‘Apache’. It was an offshoot of the P-51 Mustang fighter originally ordered by the RAF. The USAAF ordered 500 units of the A-36A Apache, with the first aircraft delivered in October 1942. All were pulled from front-line service in 1944. Total combat losses of the A-36 Apache came in at 177 aircraft.
Wartime statistics
Between 1941 and 1945, American industry built 276,000 military aircraft. Those not taken into service by the various aviation elements of the American military services such as the US navy and US Marine Corps were provided to wartime allies. The Soviet Union and Great Britain received the largest number of American-built military planes during the Second World War, totalling approximately 43,000 units.
At its maximum strength in mid-1944, the USAAF had almost 80,000 aircraft. Of those, approximately 40,000 were classified as combat aircraft. By comparison, in December 1941 when the United States officially entered into the Second World War, the USAAF had only 12,300 aircraft including around 4,500 combat types.
The USAAF would lose to all causes 65,164 aircraft during the Second World War. That number breaks down into 43,581 lost overseas and another 21,583 lost in training accidents within the United States, averaging out to forty planes per day.
The human cost to those who served with the USAAF between 1941 and 1945 was immense. A total of 88,119 airmen were killed during America’s time in the Second World War. Of that number, 52,173 were attributed to combat. Approximately 40,000 became prisoners of war (POWs), with another 12,000 listed as missing in action and presumed killed.
The USAAF claimed the destruction of 40,259 enemy aircraft between 1941 and 1945, with 29,916 of those belonging to Germany and its allies. In the PTO, the USAAF claimed the destruction of 10,343 Japanese aircraft.
