A Foreign Release Agreement was made between Lockheed and the Air Corps on April 12, releasing this model for export, providing that the Army’s P-38s would add the pilot and gas tank protection incorporated in export planes, and that Lockheed would deliver, in 16 months, a new prototype to be designated XP-58. All this, stated the Agreement, “without any additional expense or cost to the government”; presumably the company expected to pass these costs on to the foreign customers.
The Joint Purchasing Commission ordered 667 export models on June 5, 1940. This very expensive commitment would later be regretted by the RAF, which named the Lockheed “Lightning I” and inherited the entire amount after France capitulated to Germany. Addition of armor and leak-proof tanks would increase the gross weight to 14,467 pounds, and performance with the C-15 engines was very disappointing.
The armament originally considered in 1937 involved a Hotchkiss 25-mm weapon, but when this did not materialize, the prototype was to get one of four Danish 23-mm Madsens the Army imported, although guns were never actually fitted to the XP-38. On the YP-38, two .50-caliber with 200 rpg and two .30-caliber guns with 500 rpg, were specified just as on the early P-40, but below them was a 37-mm M-4 with only a 15-round magazine. An August 5, 1940, order changed all four machine guns to .50-caliber on all later P-38 models, and provided pilot armor.
Since tests on Hispano 20-mm guns, which began arriving from France by February 10, 1940, were favorable, and this gun had been selected by the British for their fighters, the 20-mm M1 was ordered into U.S. production for 607 Army Lightnings contracted for on August 30, 1940. Army and British Lightning models were to be produced concurrently, with similar armament and numerous details simplified for mass production.
Shortly after Spitfires and Hurricanes broke the back of the German bomber offensive in the Battle of Britain, the first YP-38 was flown on September 18, 1940. It is fortunate that this victory could be won without recourse to U.S. fighter production, which that month was limited to 114 P-40s, with one each of the YP-38, YP-39, and YP-43. Only the Lockheed outperformed the British types.
The first YP-38 was retained by the company for developmental testing, the second went to Wright Field on January 28, 1941, while the third and fourth were delivered to Patterson Field in March. Examples then went to Chanute and Lowry, but the seven remaining YP-38s went to Selfridge Field by May 29 for service tests by the 1st Pursuit Group.
From June 20 to August 15, 29 P-38s followed, also with V-1710-27/29 engines and B-2 turbosuperchargers, but with four .50-caliber guns, the 37-mm M4, 3/8-inch armor, and camouflage paint. Another P-38 was held back for completion with the pressurized cockpit planned for the XP-49. That unarmed aircraft began tests as the XP-38A in May 1942, but no B or C model ever appeared.
Self-sealing fuel tanks, reducing capacity from 410 to 300 gallons, were introduced on the P-38D. The first of 36 was accepted on July 1, while the rest were delivered from August 9 to October 1, 1941, completing that contract eight months late. These aircraft cost $80,311 each, compared to $30,800 for the less-capable P-40s delivered the same time.
Tests had begun in August on the first British 322-61 Lightning I with the C-15 medium altitude engines and both propellers rotating in the same direction, which were scheduled to be replaced, beginning with the 144th ship in April 1942, with turbo-supercharged power plants on the Lightning II version. The second Model 322 was accepted October 8, but later 322s coming out of the factory were refused acceptance by the British because of their poor high-altitude performance.
Standard Lightning armament on the RAF’s Model 322, the AAF’s P-38E, and on all later models, was one 20-mm gun with 150 rpg and four .50-caliber guns with 500 rpg. There were 188 pounds of cockpit armor and a 20-pound armor-glass windshield. Another 1,000 Lockheeds were ordered by the Air Force on October 31, 1941, and the first P-38E was delivered November 16.
When the United States entered the war, the only pursuit group with Lightnings was the 1st, which left its twenty-year home at Selfridge on December 8, 1941, to fly to San Diego. With six YP-38, 23 P-38, and 19 P-38Ds, they became southern California’s air defense force, joined by the 14th Group as P-38Es replaced that unit’s P-66s early in 1942.
The British allocation of Lightnings was eliminated and 143 Lightning Is were taken as “P-322” by the Army. Three P-322s were shipped to Britain for evaluation in March 1942. Air Force pilots found P-322s nose-heavy, unable to keep formation with regular P-38s over 12,000 feet, and therefore suitable only for training. The 524 Lightning IIs scheduled were absorbed into AAF P-38F and P-38G contracts, and 120 P-322s had their engines replaced later with Allison F series power plants.