In early 1937 the US Army Air Corps announced a design competition which was intended to lead to the procurement of a long range interceptor fighter, one which would have the capability of attacking enemy aircraft at a considerable distance from its base and of outperforming them at high altitude. The specification called for a maximum speed of 360 mph (579 km/h) and the ability to climb to a height of 20,000 ft (6095 m) within six minutes.

At the beginning of 1937, when Lockheed received the USAAC's Request for proposals, the company had no previous experience in the design or construction of military aircraft. This, at first would seem to be a disadvantage but in this particular instance is was probably the reverse, for it enabled H. L. Hibbard and his design team to look at the project objectively, without any preconceived ideas. The result was a solution that at the time was little short of revolutionary. The design team after conducting several tests, confirmed that no single engine then in existence could provide the speed and rate of climb required by the specification, but that two engines almost certainly would, at the same time providing a better payload margin for armament and fuel.

Having decided on a twin engine configuration (then a radical concept for fighter design) the designers were faced with the problem of how best to mount the two engines. Among the possibilities which they considered were conventional wing mounted engines, in both tractor and pusher arrangements; engines within the fuselage driving two tractor propellers via co-axial shafts, or wing mounted propellers via a complex transmission; a twin boom structure between which could mounted a central nacelle with push and pull engines. This last proposal was the most attractive, for if the tail unit was designed to link the aft end of the booms the resulting structure could be comparatively light in weight and yet immensely strong; and why not put the engines in the forward end of the booms and the pilot in a central nacelle?

This was the basic layout of Lockheed's Model 22, details which were submitted to the USAAC in the spring of 1937. On 23 June 1937, the company was awarded a contract for the construction of a prototype under the designation XP-38, and was also required to construct a mockup to finalise equipment and cockpit layout to the requirements of the Army Air Corps. Following inspection and final approval of the mockup Lockheed was able to begin detail design, but it was not until just over a year later, in July 1938 that construction of the prototype was started. Rolled out just after Christmas that year, with engine ground tests being made in early January, the XP-38 was flown for the firt time on 27 January 1939. The powerplant consisted of two 960 hp (716 kw) Allison V-1710-11/15 inline engines, these being "handed" so that the propellers rotated in opposite directions to neutralize engine torque. In this configuration when viewed from behind the port propeller turned clockwise.

Initial testing of the XP-38 progressed well, so well in fact that on 11 February 1939 the aircraft was dispatched on a transcontinental flight from March Field, California to Mitchell Field, in New York, a journey accomplished with two en-route refuelling stops in 7 hours 2 minutes. However, this breathtaking performance was to end in disaster, for as the result of an undershoot on the final approach to Mitchell Field the XP-38 was damaged so severely that it was a write-off. Fortunately, earlier testing and the trans-America flight had given some indication of the potential of the design, so that the USAAC had no qualms in ordering a service test batch of 13 YP-38s on 27 April 1939, and followed by the first production order for 66 P-38s on 10 August.

As a result of the early tests it was possible incorporate certain modifications to the pre-production aircraft (Lockheed Model 122), this including the introduction of 1,150 hp (858 kW) V-1710-27/29 engines, installed with propeller rotation opposite to that of the XP-38. In addition, the nose mounted armament was changed from the 23 mm cannon and four 12.7 mm (0.50 in) machine guns of the prototype to one 37 mm cannon, two 12.7 mm (0.50 in) machine guns and two 7.62 mm (0.30 in) machine guns. There was, however, a long wait before the first YP-38 flew on 16 September 1940, the aircraft being handed over to the USAAC for evaluation in early March 1941; all 13 YP-38s had been delivered by early June.

There was little doubt that Lockheed had produced a remarkable aeroplane, for early testing showed a maximum speed of 405 mph (652 km/h) at 20,000 ft (6095 m), an altitude to which it could climb within the required 6 minutes. One major problem was discovered during service trials, namely buffeting of the tail unit, and early attempts to eliminate this by the introduction of upswept booms, to lift the tail unit above the disturbed airflow aft of the engines and wings, were completely unsuccessful. The solution lay in an adjustment of tailplane incidence and changes to elevator mass balancing, these modifications being incorporated on the last 36 aircraft of the first production order, which were designated P-38D.

The first 30 production aircraft were delivered as P-38s (Lockheed Model 222), with delivery starting in mid-1941. These were generally similar to the YP-38 but had armament much the same as that of the prototype (except that the 23 mm cannon was replaced by one of 37-mm calibre) plus the provision of armour protection for the pilot. Their basic structure was typical of the whole family of P-38s which were to follow, with production continuing throughout World War II until terminated finally by the contract cancellations after VJ-Day. Of all-metal construction, the wing was mid-set and consisted of a centre-section on which was mounted the central nacelle structure to accommodate the pilot, and nosewheel unit when retracted. Mountings for the engine nacefies/tail booms were integral with the wing centre-section structure, and outboard of these were the wing outer panels. Fuel tanks were housed in the wing centre section, and trailing-edge flaps of the Lockheed-Fowler type were installed. The tail booms, which could be considered to start from the fireproof bulkheads aft of each engine, provided housing for the main landing gear units when retracted, the General Electric engine turbochargers, cooling radiators and, at their extremities, the twin fins and rudders; they were rigidly braced together at the aft end by a continuous tailplane structure, with the single elevator inset in the tailplane trailing edge between the rudders. The powerplant comprised two Allison V-1710 inline engines, each driving a constant speed and fully feathering propeller.

The P-38s were followed into service by the 36 P-38Ds, beginning in August 1941, and these could be regarded as the first combat-worthy examples of the P-38. In addition to the tail unit modifications mentioned above, they were provided with a low-pressure oxygen system, a retractable landing light, and self-sealing fuel tanks. The gap in designations between P-38 and P-38D is accounted for by a single XP-38A (Lockheed Model 622) prototype with a pressurised cockpit nacelle, while the P-38B and P-38C identifications were allocated to projects which failed to materialise.

The P-38Ds were also the first to bear the name Lightning, which was the designation allocated to this aircraft when ordered for the RAF by the British Purchasing Commission of 1940. Some 667 were ordered, these being Lockheed Model 322s, and either because of an oversight on the part of the Commission (and this seems the more likely explanation), or because of an export ban on the engine/turbocharger combination, the first three examples, supplied to Britain as Model 322-61s, were considered to have inadequate performance when tested and the entire order was cancelled. These Lightning Is, as designated by the RAF, had two 1,150 hp (858 kW) Allison V-1710-C15 (R) engines without turbochargers and, as indicated by the R suffix, both were of right-hand rotation. Testing by the USAAF, following their acceptance of the 140 outstanding on the first British order, confirmed the RAF's findings and they were used only for various training and experimental purposes under the designation P-322. The balance of 524, representing the second British order, which were to have had the standard P-38 engine installation (Lockheed Model 322-60 and allocated the British designation Lightning II), were absorbed into USAAF contracts and were produced as either P-38F or P-38G Lightnings.

The P-38E was the last version to enter production for the USAAF before the attack at Pearl Harbour, and the type differed from the P-38D in having changed electric and hydraulic systems, the 37 mm nose cannon replaced by one of 20 mm calibre, and the provision of additional ammunition capacity for the nose guns. Some 210 of this version were contracted, but before they were completed 99 were converted for a photo-reconnaissance role under the designation F-4, with the nose armament replaced by a cluster of four cameras. In a similar manner, 20 of the ensuing P-38Fs were converted as photo-reconnaissance F-4As, but the 507 P-38Fs, which began to enter service in February 1942, had a number of changes which were introduced progressively to different production batches. These included the installation of 1,225 hp (913 kW) V-1710-49/53 engines, changed oxygen equipment, and the provision of so-called 'manoeuvring flaps'. In fact, these were the standard trailing-edge flap installation, but a readily-selected setting of 8 degrees extension made possible much tighter turns. Provision was made also for the carriage of external weapons, and racks beneath the inner wings could accommodate two 75 or 150 US gallon (284 or 568 litre) drop tanks, 1,000 lbs (454 kg) bombs, 22 in (559 mm) torpedoes, or smoke producing installations.

By this time, of course, USAAF Lightnings had become actively engaged in the war, and a P-38 of the 50th Fighter Squadron, a unit of the 342nd Composite Group based in Iceland, recorded the first operational success for a Lightning a few days after arriving on the island on 14 August 1942, destroying a German Focke-Wulf Fw 200 Condor over the Atlantic. In November 1942 P-38Fs saw their first large-scale use during the North African campaign. Their wholesale destruction of German cargo and transport aircraft over the Mediterranean quickly earned the nickname 'der Gabelschwanz Teufel' (the fork-tailed devil) from the Luftwaffe, but in this theatre also came the first appreciation that in its intended fighter role there were shortcomings. Not only was the wide span, twin-engined P-38 less manoeuvrable than the Messerschmitt fighters against which it was in combat, but it did not take long for Axis pilots to discover that high performance was limited to high altitude. If the P-38s could be forced to fight at altitudes between 10,000 and 15,000 ft (3050 and 4570 m), then the margin of performance was in favour of the enemy's Bf 109s.

A Lockheed P-38J Lightning of the 27th Fighter Squadron 1st Fighter Group 15th Air Force US Army Air Force - Salsola Italy 1944

Prior to the above encounters, however, the next production version had begun to enter service, during June 1942. This was the P-38G (1,082 built), which introduced the 1,325 hp (988 kW) V-1710-51/55 engine. Improved turbochargers, oxygen system and radio were incorporated at various stages throughout the production run. Of the P-38G total, 181 were converted for a reconnaissance role as F-5As, and because the V-1710-51/55 powerplant tended to overheat, an additional 200 F-5Bs were provided with intercoolers. With larger numbers of P-38F/-38Gs becoming available, the type was soon in service with USAAF squadrons in all theatres. In August 1942 the lst Fighter Group's 71st and 94th Fighter Squadrons arrived in England after ferrying their aircraft across the Atlantic, and were joined almost immediately by the 37th, 49th and 50th Squadrons of the 14th Fighter Group. The 94th Fighter Squadron was, incidentally, the famous 'Hat in the Ring' squadron which had fought alongside the Allies in Europe during World War I.

The last 200 P-38Gs off the production line introduced underwing racks with a combined stores capacity of 3,200 lbs (1451 kg), and this became standard on the P-38Hs which followed. Production of this version totalled 601, of which 128 were converted for photo-reconnaissance duties as F-5Cs. All had 1,425 hp (1063 kW) V-1710-89/91 engines, and late production examples had improved turbochargers. There were, however, extensive changes in the P-38Js (Lockheed Model 422) which followed, for the wider use of P-38s in zones where high temperatures were commonplace had made it essential to eliminate the engine overheating problem. This resulted in the introduction of 'chin' radiators at the base of the engine nacelles, enabling this version to develop its full take-off power to a height of 26,500 ft (8075 m). Other progressive improvements included increased fuel capacity; the introduction of small electrically-actuated dive flaps, beneath the undersurface of the outer wing panels, to overcome a nose-down pitching movement at high speed; and in the first application of power-boosted controls to a fighter aircraft, the provision of hydraulically powered aileron boosters which required the pilot to provide only 17 per cent of the force needed for aileron operation. P-38J production reached 2,970, and this version was in extensive use by early 1944.

Three P-38 fighter groups were operational in the Pacific, where Lightnings were accredited with the destruction of more Japanese aircraft than any other fighter in USSAF service. They are well recorded in the air force's history for a string of memorable actions, including the interception and destruction, some 550 miles (885 km) from their base, at Guadalcanal, of the Mitsubishi G4M carrying Japan's Admiral Isoroku Yamamoto, a skilful action carried out by aircraft from the 70th, 112th and 339th Fighter Squadrons. And, of course, the USAAF's 'ace of aces' of World War II, Major Richard I. Bong, scored all of his 40 confirmed victories while flying P-38s in the Pacific theatre. In Europe P-38s served mainly with the 9th Air Force, used extensively on long-range fighter escort duties in support of 8th Air Force daylight bombing missions against German targets.

There were no production P-38Ks, the designation XP-38K being allocated to a single P-38J powered by Allison V-1710-75/77 engines with larger diameter propellers, and this was followed by the most extensively built version, the P-38L. Lockheed produced no fewer than 3,810 of the model, while an additional 113 were built by Consolidated-Vultee: the P-38L differed from the P-38J in having 1,475 hp (1100 kW) V-1710-111/113 engines which had a combat rating of 1,600 hp (1193 kW) at 26,500 ft (8075 m). Some batches of this version had a mounting, dubbed 'Christmas tree beneath each outer wing panel for the carriage of five 5-in (127-mm) rocket projectiles.

Well over 700 reconnaissance aircraft with the designations F-5E/-5F/-5G were converted from P-38J/-38Ls, and 75 P-38M night fighters were also derived from P-38Ls. These latter, used operationally during the closing stages of war in the Pacific, carried a radar operator (seated aft of the pilot), his equipment, and retained the full weapon load of the P-38L. Variants of the P-38 included some P-38Js modified in Europe to serve as 'lead-bombers' or 'Pathfinders'. In these aircraft the standard nose was replaced by one with a bomb-aimer's position, which had a transparent nose, while others for a similar role carried BTO (Bomb Through Overcast) radar in the nose, making it possible to attack a target that was obscured by cloud. There were also a few TP-38L two-seat trainers derived from P-38Ls.

With the end of the war and the inevitable cancellations after VJ-Day most of the USAAF's Lightnings rapidly disappeared from the scene, but a few F-38J/-38Ls remained in service until 1949.

Nicknames: Fork-Tailed Devil; Pathfinder (P-38L carrying a nose-mounted Mickey radar.)

Specifications (P-38J):

Engine: Two 1475hp Allison V-1710-111/113 V-12 piston engines
Weight: Empty 12,800 lbs., Max Takeoff 21,600 lbs.
Wing Span: 52ft. 0in.
Length: 37ft. 10in.
Height: 9ft. 10in.

Performance:
Maximum Speed at 25,000ft: 414 mph
Service Ceiling: 44,000 ft
Normal Range: 450 miles

Armament:
One 20-mm cannon in nose
Four 12.7mm (0.5 inch) machine guns
Two 1600 lb. bombs

Number Built: 10,037

Number Still Airworthy:  ~7